Engine ideas please....

[CLASSIC87']

So I'm looking at putting another engine in the 82' Blazer. Right now it appears it has a mild 305 with bottom end work already done previously. Currently I changed the main bearing and rod bearings and the crank showed signs of some overheating, scaring, etc. I'm still having a knock in the #2 piston so I'm looking at replacing the whole thing.
Here are a few of my question:
1. If I buy a rebuilt long block; will my current Eldenbrok manifold, carb, acc brackets, etc bolt up to a 350 block?
2. Is it a mojor task to install a TBI set up in it?

I'm just starting to research this... I'm pretty new to the whole "engine" side of things... my budget is about $1500 with my dad/brothers and I doing the labor part. Also I'm looking for gas mileage... not just torque etc.

Any suggestions?!

Thanks as always!
Anthony