For wheels which are much more readily available, consider fitting Volvo rims to the Twin Cam spider. They are a loose fit - maybe 1mm oversize, easily packed with sheet metal prior to welding and not too great a gap to bridge. The wheels to use are Volvo 164 sedan 15" X 5" wide or 165 wagon 15 X 5.5" wide. These are a modern safety style rim with the bead groove for tubeless tyres and therefore do not look entirely original. It may be a bit embarrassing to admit to using Volvo parts on an MGA but it is a convenient source.

On 12/26/2015, Peter Todd in Australia with Twin Cam YD2/2435 wrote:
"Fitting wider rims to my twin cam centres. I bought four Volvo 5.5 inch X 15 inch steel rims. I mounted the Volvo rims in an old 2 metre gap-bed lathe and machined out the large spotwelds holding the rims onto the centres. The twin cam centres are not welded to the rims but rivetted. The first wheel I linished [ground] the tops off the rivets, but then on the other three, I saved about 1/4 of an hour on each one, by drilling a pilot hole in the centre of each rivet and used a cobalt drill to drill off the heads of the rivets on the rim side of the wheel. I had to cut the twin cam rim off using a 1mm X 125mm cutting wheel on an angle grinder. Cutting across the rim, I did not to have to fully cut through the rim as when the rim thickness got down to about 20 thou, the rim popped apart enabling me to take out the centres without marking the centres with the cutting wheel.
"The problem I now face is how to mount the 5.5 inch rims on the twin cam centres, as the rims are an interference fit on the centres. Do I have to heat the rim as per fitting a flywheel ring gear? or do I bite the bullet and let a roadwheel Specialist finish off the job. I have had twin cam wheels widened by a wheel specialist before but on this car so far I have done everything myself, and would like to continue to do so"!

On 12/26/2015 -0800,Dirk Vanussel wrote:
"Had the same problem with TR wheels. I then took a center and went trough all the wheels I could possibly find at breaker's yards. In the end a Honda (think Accuro) rim fitted. But these are unobtainable to find now. The second set was made with (you will not believe) rear wheels from a Smart! The centers were a loose fit but with a added layer of 1 mm metal it now works perfectly".

On 12/30/2015, Peter Todd wrote:
"Finally finished. Packed the centres in dry ice overnight. They had reduced their diameter by 1.5 mm the following morning. I could then start the centres into the rims from the inside of the rim. Using a vernier caliper with the depth gauge I was able to gently push the centres in a garage press into the correct position to give me an extra 1/2 inch outside offset. I measured the distance from the outer face of the rim with the rim sitting outer side down through the numerous holes in the centre perimeter on the dining room table. The measurements through the holes to the table top varied by only .43 mm. Centres now welded to the rims.
"Anyone contemplating going down this track using Volvo 5.5 inch rims, be warned – there are two types of Volvo 5.5 inch rims. The ones with the enormous square spot welds will give you an interference fit with the MG rims. The ones with the large round spot welds will give you an oversize rim, that you may have to use shims to mount the Volvo rim on your Twin cam centres. The easiest route is to use the wheel with the square spot welds holding the Volvo rims to their original centres as they can be more positively located centrally on the Twin cam centres".

On 12/30/2015, Mark Hester wrote:
"I've always been told TR6 rims were used. When my brother did his car a model of 4 wheel drive wheels were used to make his 6 inch rims. They were too wide and much to heavy but did easily take 205 racing tyres.


On 12/8/2021, Franco de Piero wrote:
"Why the Volvo 164 wheels, since all the center part of the Volvo wheel gets discarded and only the very rim is used? Can you kindly put some more description on how this was done? Why Volvo 164 wheel? Does that have something to do with offsides dimensions that only that wheel has it compatible with MGA"?

This article mentions two different Volvo wheels, commonly TR6 wheels, and also a wheel from Smart car. Not that other wheels can't be used, but these mentioned are wheels that have so far been used successfully.

The trick is to fond a wheel with the same inside diameter on the rim that can mate closely with the Twin Cam wheel center.diameter If you were looking in a bone yard for compatible wheels, take along a large caliper to measure prospective wheel accurately. If the replacement wheel rim is 1/8-inch too small it will never go together. If the replacement rim is 1/8-inch too large you will need shims to space out the difference before welding together.

Next issue is wheel offset which is commonly near zero for larger cars, but is a substantial positive amount for the MG. These wheels are dished out a lot, much like wheels for a front wheel drive car, so wheels vary some in that respect. Wheel offset is at least partly "controlled" by the rim design where the inboard part of the rim will likely be wider than the outboard side.

Then you get a choice of older J-type wheels with a smooth rim, or newer wheels formed with a groove on each side to make a modern Safety Rim These definitely look different on the car. I have run vintage J-type wheels for more than 50 years without any problem, including lots of competition driving. The safety rim can have some small advantage if you insist on driving with less than 10-psi air pressure in the tires (half flat squatty tires or near fully flat). But you would surely notice bad handling of the car before pressure gets that low.

So yes you could use replacement rims other than the ones mentioned, just that you get to do the development work to determine if some other rim would be compatible with the Twin Cam wheel center and giving the rim width and offset you desire.