I would use either a Autolite #3923 or 3924. Champion # RC9YC or RN9YC, The C series plugs use a 5/8 inch spark plug body and the N series use the original 13/16 socket size and body. The R stands for resistor type plug, which is what you want to use on a street motor
Both of those Autolite plugs are resistor type also, the 3924 is a little hotter heat range than the 3923 is
It is always safer to use a colder plug when tuning a new motor than to hot of one, I would try the #3923 first and go from their
The colder plug will get blacker quicker andtry to foul out than the hotter plug will so try the new colder set first gapped at .035 or wider up to .050 and see if they are running clean or getting to brown or black from being to cold.
Then go ahead and try the hotter plug next and look at them and decide after that which one you want to run in the motor full time