Triumph 2500PI v TR6

[Steve Trident]

Hi, I have a 2500PI engine and manual gearbox fitted in my Trident. The chassis is modified TR6. The engine number is MG21711HEBW, with a type 516816 head. The car was registered Feb 72 but the engine could be earlier. My question is to what extent are engine and gearbox parts interchangeable with those of a TR6 .
As a second question does anyone know what date my engine number would have been produced.
Thanks

[Steve Trident]

Thanks to both. Just to clarify: I'm not thinking of changing to a TR6 engine. I need to do some work on my existing engine and while I can get what I need from Moss for TR6 specification I wouldn't know where to go for specifically 2500PI bits.