will a stepside longbed bed bolt on my longbed fleetside

[dragn91]

So I've been on the hunt for a good bed and wasted 75 Bucks on one I didn't check out enough that ended up to be junk but I came across a 1973 longbed stepside that's had a camper on it it's whole life. Wile I really only need the bed I'm gonna buy the whole truck for 400 it's rusty up front but the beds great except some light rust on one fender. What I need to know is will any longbed bolt to any long bed or are they different? Mine is a 1980 the beds off a 1973. Mines a factory fleetside this one's a factory stepper. Also does anyone know if the 73 c20 had 307s or 350s or eaither from the factory as I might freshen up the engine and use it as well.