[V]

cracked head or cracked header are two very different issues. Due to the oil contamination problem, I will assume you mean cracked head. In my opinion, $2500 or $3500 to fix a cracked head(singular as in only one side) is quite overpriced.
But I also doubt you cracked a head. The most likely problem is that you had a head gasket blow, or basically fail. That allows oil and antifreeze to mix between the block and the head. To fix a bad head gasket, is a few hour job but even that I do not think it would come near 3,500. I'd say take it to a different , or recommended mechanic and get a second opinion.

Also people who suggest a 383 small block, if its not an LS-based 383('97-'04 era engine) don';t even bother. Most people talk about 383 engines that are gen 1(1st generation) small blocks that range from like the '60s-'90s. It would be more trouble to try to convert the car to take the older engine. You can buy ls-based performance engines that are ready to go with 425hp or more but you are looking at like 7,000 plus install and then you really should upgrade the rest of the car to handle the power increase otherwise you'll break more stuff.

For $3,500 you might be able to get a decent heads and camshaft package installed, and you'd be making over 425hp from the engine.