Measured out radiators. Found a 1R948 radiator that fits an Audi 5000 88-85 2.2 L5 MT. core size 24/1/4" (Len )*12/1/8"(wid)*1/7/8"(depth), and side tanks are 2/5/8"(depth) * 12/1/2"(height). This radiator has the inlet and outlet hoses on the passenger side. The lower outlet is located about 3-4 inches from the base, which will hopefully clear the steering rack on the MG. There is no radiator cap, so an external header tank will be needed. A water temp sensor fitting is located on the passenger side, below the lower hose. Phone number to order (in Northern California) is (800) 225 6296. I will most likely try to find a used radiator in a wrecking yard. Radiator 1R947 is very similar to the 1R948, all dimensions are identical execpt the core length of the 1R947 is only 22/1/2 inches long.
** other radiators may fit by mounting them backwards and having hoses exit facing away from the engine. VW radiator 1R604 (20/5/8"*12/1/2"*1/1/4", assorted rabbits 77-82, has rad. cap) and 1R633(21/1/2"*12/1/2"*1/1/4", 80-82 pickup, some diesel rabbits 77-80, no cap) may also work.
** note The stock RX-7 radiator is about 21"*16"*1.5"
6-18-98 bought the Audi Radiator for $100 bucks used. I also bought the matching expansion tank and a new cap, both for 5 dollars.