[Xeen]

Honestly the metallurgy in the new crate motor is so much better than the old 60's-70's small blocks it's not even funny, you have the better deal with what you have you just need to figure out a solution and trust me it's out there.
You will burn up your spark plug wires very quickly unless you shield and route them properly then you will definitely be unhappy, don't give up so easily.
The local machine shop will know in 2 seconds what heat shields you need with that block/exhaust manifold combination so load up the engine and take it down there, they will probably even have them in stock and sell them to you.