Will they work on gen 5 ???

Maybe. The deck and head surfaces don't always match up that well and they will leak coolant into the lifter valley. I have a set of 049's on a gen v block, I made a paper template of the heads and water passages and matched it to the block to make sure they would seal.

What would be the number of a large ovel port or a good square port head to fit a gen 5.Not over 5200 rpm

14097088 1991-up 454/502
The part number above is what your long for

And for future reference,here's a list of the castings

http://www.minuit10.net/EngineCode/c...linderHead.htm

I think I saw a gasket that would allow the head to work...look thru felpro's site

Put alot of 049s and 781's on gen 4 454s with reasonable cams and they pull great to 5400 or so .
its been on my bucket list since gas was a buck a gallon to swap some peanut ports with 049's on mercs "310 at the the prop" gen 5 and see what happens, there are gaskets just for that swap but you still should confirm it aligns properly .and no edelbrocks with adapters please on your induction change up

Yes, there are gaskets that work, but you can still have an issue. The problem is the difference in the water passages on the head and block. All the castings are not exactly the same, some have them in the right places that allow at the gasket to crush and seal, others miss and you will get no crush and leak into the valley. The ones that make it are very close.

Yep . No dirty casting flash in your heads , measure mating surfaces with a real straight edge , tee a gauge next to your t stat and keep it a clean 12 psi or so at full boogie , and pop your block plugs and suck the sand and silt out of the bottom if not done already , and go enjoy some healthy midrange punch