The s/r heads will bolt up to your stock parts, but I assume that you will be getting an aftermarket intake manifold when you buy the new set of heads anyway. From what I have seen, the Vortecs will make more hp and torque than the s/r's. I had a 355 with vortec heads and I loved it. Below is a website that has alot of different engine combonations so you can compare the heads you are looking at and make your decision. If you buy the vortecs, buy them from Scoggin Dickey. You would need to get the heads with the upgraded spring package which will require machine work. Scoggin Dickey offers a set of Vortec heads with the machine work and springs that can handle up to .525 lift for $635 for the assembeled set.