Newbie with questions on engine build

I have a very nice 77 Lincoln Mk V with a 460/C6 combo. I want to uncork the power of the engine so the car will move the way it should rather than the asfixiated lump it is now. I looked at the proven builds and the builds for the 400-425hp & the 425-450hp look like a good target for my purposes. Although no torque figures are given for these builds I think either one of them will exceed my 500ft/lb target.
What is the availability of the D0VE heads? After all, they have been out of production for more than 40 years. Or is there an aftermarket version of these heads?
Thanks

what kind of budget do you have?

A set of DOVE heads are a good start for getting some compression.

Another big upgrade for those cars is gearing.

You are right gearing would be a good place to start. That leaves my question about the DoVE heads availability. I don't see any on eBay at the moment (there is pair of damged ones) and considering that production ended so long ago what is the likelyhood of scoring a pair of DoVE heads?
I've seen the Ford Racing SCJ heads but I think they may be more suitable to a more aggresive built than I have in mind.
Budget, what budget! Don't get me wrong money is definitely a consideration but unless I can price all the parts and machining services I won't know. Hence the question about the heads.
Thanks

Dove heads are still around I have 2 sets a set of dove-a and a set of dove-c. If you need a set both set complete the dove-a are bone stock and need to be reworked the dove-c have had work on them and are set up for .650 lift with port work and set up for roller rockers.