i am running a 351w from, what i was told was a 77 e150 ,

engine was rebuild with new cam edelbrock intake and edelbrock carb,and a cam(it was a summit racing kit i was told) i recently noticed a miss that was very inconsistant so i decided to upgrade the ignition system with a ready to run distributor from msd, msd coil and msd wires, when i went to the local autoparts store they pulled a set of autolite #25 plugs (5/8 spark plug small threads)stating that is what fit in the van, got home pulled the first plug and it is a #45 (13/16 big thread plug)

i want to go with a better plug but i dont know where to even start

i know since going to autolite.com and a few other sites it is confusing

i heat ranges sizef different manufactures ect,
i know the stock 45 plug in a e150 was no way designed for the cam, intake, headers and ignition system and i want to get the most out of my set up

ant help would be appreciated

 

bump

 

I run 45's on a 302 that is much more built than what you have. They work just fine.