Crate engine or rebuild 1974 350?

[chevybill]

Hey guys, I am looking at the 260 or 290 horse gm crate engines for my truck and I know where there is about a 1974- ish half ton with a 350 engine and some type of auto tranny.

Should I try to get this engine and possibly tranny for a rebuild or should I just go with a crate engine?

Is this older engine better as far as the head and block than the new engine?

This truck has not ran in at least 15 years and of course the block and heads could be cracked, if they are good is this early 70's engine and tranny worth the trouble, I know they are original to this truck.

How does the old saginaw 3 speed tranny work with these engines, I have 3.73 gears and feel like I am going to be running some serious rpm's at highway speeds.

Thanks for your replies.