Ive got a 130 strada abarth engine in my 131 (well its actually out at the moment).
From what i understand the difference appears to be only in the crankshaft end's. Having said that im sure their may be some internal differences.
As for taking the engine from a 130TC and putting it straight into a 131 RWD car, why not? mine still has the FWD sump on, engine mounting points are the same, only modification needs to be the input shaft of the RWD gearbox. This is the subject of discusion on ANO www see:
http://guy-croft.com/viewtopic.php?t=720 If your thinking of putting a 130TC engine in a 131 drop me a line and ill try to help where i can.
Please correct me if im wrong.
Steve