Thanks for getting back to me. I looked up those pistons and they are a budget buster using that 4.250 crank. So please let me know if these options i got in mind are correct or not.

a- 454 standard crank with 6.535 rods 454 pistons with ch of 1.645 gives me a minus deck clearance more or less -0.02, instead of decking it below zero can i just get a slight dome on the piston to make up the difference and at the same time adjust the compression? that way i don't have to readjust everything else.

b- 454 standard crank with 6.385 rods 427 pistons same thing here i get a -0.05 deck clearance can i get a domed piston to make up the neg. deck difference and adjust the compression?

c- 427 standard crank with 6.535 rods 427 pistons. again here if i use 1.765 ch pistons i get a neg of -0.02 can i dome here also.

d- 427 standard crank with 6.535 rods 454 pistons with 1.645 ch pistons neg deck height again but a tad to much at -0.14. can i dome there or do i have to deck the block -0.10 and make up the difference with the dome and if i deck it at -0.10 how much do i really have to adjust everything else.

how far`below the deck can one go safely without creating a situation were the compression ratio is just way to low. or can like mentioned earlier used domed pistons to make up for the compression lost?

I have aluminum merlin heads i got from a friend who owned me cash for remodeling work i did for him. they have 119cc chambers, rectangle port runners large valves