With a used engine and required quality machine work you will be hard pressed to build a engine for 1500.00
If your budget is 1500.00 purchase a NEW GM crate 350.
You can find them at most Gm dealers, it's like a car, shop around. You will find your best deal at a GM dealer that is a level one power-train dist.
Or order from summit, and sometimes it's cheaper if no sales tax.
You can make performance changing things in time as funds become available.
The engine will be virgin new! And have a 3yr 100k warranty.
Or!! Save up a few hundred and purchase a 350/290hp engine
Absolute best band for the buck. 2yr 50k warranty