HELP! I'm new.I have questions..

[needadually]

Hi Folks, I need some advice. I presntly own an 88' GMC Rally STX van with a 305 c.i. BUT I need a bigger truck so I can tow. I want a 350, because the 305 runs out of steam when loaded.
I found an 86' Sierra Classic, Trailer special, one ton dually with an auto. trans and a 350 c.i. There is also a class 5 hitch.
The problem is that the engine is bad, and the body is worse!! so, Is this a good restration candidate? Is the above a bad combination?? and last .. where do I look for body parts. I suppose here is a good start.
For sure, I will need both doors, both inner fenders, rockers, floors, RR glass dually fender. A box would be nice, or at least new panels etc.....
By the way, I can buy it for about $700 USD. Is that good or bad?
Ok, soory for all the questions, but a reply would be VERY much appreciated!!!
Thanks!!!