Rebuilt short blocks
A nice rebuild on that shortblock shouldnt cost more than $1500 unassembled. You could prob go cheaper than that if you had to depending on parts. My feeling is, if you can get a decent job for 50% more than the best mass rebuilt, then rebuild yours. Because it will take at least that much in time and aggrivation to get things corrected when it's in and doesnt work right. In your case, $6-700 (no magnum core, right?), plus the $2-300 in gaskets, paint, misc tune up parts, belts, hoses, etc., means you're dropping $1K on it. Going close to stock, but say using hyper pistons for decent compression, you can build one for $1400. You'll spend more than $400 fixing it. I guaranty.