'63 valiant 4 door /6 cruiser questions.

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Suggest you purchase a good cylinder head core you can build up. This way you'll have your DD while the cylinder head build up goes on.

You'll need to enlarge the valve seats for oversize valves. Install hardened seats on the exhaust valves. Also have your machine shop clean up the ports and maybe a little re-shaping if the budget allows.

If the rocker arms are in good shape, you can install heavier duty valve springs and mill the head .050". This should still let you get by with regular gas and there is enough range in the rocker arms for correct valve lash adjustment.

Mopar Parts list:

P4286785 1.70" stainless intake valve (stock is 1.50) 6 each
P4286786 1.44" stainless exhaust valve (stock is 1.36) 6 each
P4286813 valve spring for .390/.450 lift camshaft 12 each
or
P4120249 valve spring for .430/500 lift camshaft 12 each

When the cylinder head is finished, it is a simple exchange with the head that is already on the motor.