Quote: What type of cylinder head? stock cast iron or aluminum?
If stock iron eads I would use a Autolite 74 or 75, try the colder #74 first and see if it and your local gas get along If aluminum then I would try the Autolite # 65 or 85(I think the # 85 are the restior plugs in 3/4 long reach, it is the same plug used in the stock SB Mopar heads )
autolite 3924's for 3/4" reach. 85's are 3/8" reach.
I use the 3924 also for my SB which works on the BB alum heads for anything in the 10 compression range
If stock iron eads I would use a Autolite 74 or 75, try the colder #74 first and see if it and your local gas get along 
If aluminum then I would try the Autolite # 65 or 85(I think the # 85 are the restior plugs in 3/4 long reach, it is the same plug used in the stock SB Mopar heads 
