Corvette Ram's horns

[FL71C10]

I am tgetting ready to put the engine in my truck (350 out of a 75 impala) and was wonderng if the stock impala exhaust manifolds will fits, or if I should get a set of rams horn manifolds. I found someone local who will sell me a set of corvette rams horns for $50. Are all corvette manifolds better than truck rams horns? How do I know if they are actually off of a corvette? Will any of those fit my truck?

The guy also offered to sell me heat risers for $10 each. Do I need or want those?

Thanks!