Hi Guys

I am a 35 year old newbie who is just starting out in this hobby and I have a really simple question. I am just waiting for my nice new SIG LT-40 ARF to arrive (reccommended to me) and I have been offered a free OS FP40 engine which, while older, has NEVER been fired up at all (the guy who offered it to me said he got it years ago but never used it). As I understand it, the FP was the engine that the LA replaced and as such is/was OS's plain bearing economy engine. Would this engine work with the LT-40? I have spent the day looking around and have seen people recommending the likes of .46 engines and race bearing engines and I am wondering if I should forget about the FP?

Any and all input appreciated.