how much flexibility is there in swapping in a 12A engine for a 13B in an 85 GSL SE, I already have a 5 speed manual transmission from a 12A on the 13B, and it has performed fine for 6 years.

 

You can put a 13B in a 12A FB, including pre-84s, pretty easily - besides the engine, harness, and ECU, you need the right oil pan so it will fit, but it is supposed to be easy (I'll find out here in the next few months).

Therefore, I am sure you could do the reverse operation - again making allowances for the engine, harness, etc., and the correct oil pan.

Having said that, why would you want to loose 30hp and go to a smaller engine? Is your 13B bad and you have a good 12A? (sell it and buy a good 13B or rebuild yours). Do you want a carb (I consider it a step back, but a lot of people move to high-end carbs for granularity of control without a computer)?

I am sure you have your reasons, it just seems odd. Good luck

BTW, there are many threads on the 12 > 13B conversion. Read through them, it will at least give you details about the differences.

--BTC