Search this board. It has been discussed. Thomas Hackmann Built one for his ridiculously sweet project.
I'll touch some high points to let you know what you are in for... You have to drill a hole in the intake side of each head, to flow water to the Windsor style thermostat. You have to drill the Cleveland water passages on the bottom of the head into a round opening, then plug them. If you have 4v heads, there are a few choices for the intake manifold... Original, tunnel ram, Rousch, and a couple others. Most are swap meet only items. You can get single and dual 4v tunnel rams from Wieand for sure new, maybe Offy. If you have 2v heads, the parts are newer, but still hard to come by. B&A Performance made single and dual planes until a few years ago, they are swap meet now. I think Parker makes one available new. Original pistons are available from TRW. They are Cleveland style, with a deck height designed for 289 connecting rods. 302 rods are shorter and would require a different piston. Pushrods are unique. The rest of the heads use Cleveland stuff, of course. The cam would be standard SBF, you would have to alot clearance for the extra lift made by the Cleveland rocker arms. Headers are unique. Several companies do or did make swap headers. Tubular comes to mind, I had a set of their B302 Maverick headers at one time. Good stuff, but expensive. Intake manifold gaskets are unique, and still available. If this list is not discouraging to you, then give'r a try. 4v heads on there will not 'turn on' at any low rpm. 4v heads barely give streetable torque with a 351, a 302 would be very soggy at low rpm. 2v heads give good streetability, but the large combustion chambers are prone to detonation and are hard to make compression on a 302. Aussie heads, 2v with closed chambers, have the smallest ports and chambers available, but you have to hunt for them. I don't know about other headers, but the Tubular B302 headers have huge primaries... 2". That won't help torque either. They are good people though, I am sure you could order them in whatever primary you want. Dave
Should you be interested in a pair of Australian 351 heads and matching intake, I have a set of bare heads and intake with gaskets for builing a small port Street Boss. Email me for details and price.
