Welcome aboard Larry
Consider:
Kuntz & Company.
540 Unity Road
Arkadelphia, AR 71923
870-246-2595
The proprietor is Jim Kuntz. A well known 351C engine mechanic & racer. His experience and knowledge regarding the 351C are rare in this day and age. His credentials are second to none, his pricing is very fair, he's honest, he won't try to sell you stuff you don't need.
Website:
Kuntz & Co.You're going to need something other than the D3ZE head castings. Those heads have the small valves and large 78cc open chambers. I know a couple of guys racing with those heads, they've chosen them for very specific reasons, but I don't think they're a good choice for the average person. I'd suggest the big valve quench chamber heads D0AE or D1AE.