So is my 87 a 305 or a 350 from another year

[cyberpine]

When I purchased my truck a few months ago I was really surprised at how strong it was running and so pressumed it to be a 350. Later, i found out the sticker said 5.0. duh.

I just got back from the shop where I had them do a compression test, check the oil pressure and pop the lids to see what condition the engine was in.

The mechanic was very impressed with the engines condition given the year.

He is reading 200lbs of psi (on average) compression! and 80psi oil pressure. He pull up the lids and found new gaskets and a super clean heads - no sludge of any kind.

He's telling me he thinks the engine was rebuilt not too long ago or is not the original engine because of the bolts on the covers?? He's going to call a machine shop to see if he can figure out for sure.

How can I tell for sure? The oil stick is on the passenger side. The thickness of the fly wheel? The serials .. which he was unable to read.