as far as 60-70 hp. no unless you put bigger valves in it. just like you can to your heads you have. and yes you have to buy a new intake to fit the vortec heads. no comp. changes you need. you can look at summitracing.com or ebay.com and a few others to look for kits or separat pieces everybody has diff. prices. but my opion is why do all that when you can have your heads reworked with 2.02 valves a diff. cam, and a curve kit in the dizzy. and you will have more at a cheaper cost. just don't take my word for it look or other people to chim in on this.