What spark plugs to use?

[davepl]

Originally Posted by Fitz

dave:
GM 454HO requires AC Delco MR43T Resistor plug, 14 mm thread, heat range 3, Tapered seat
GM L72HP requires AC Delco R46N: Resistor plug, 14mm thread, long reach

Not worth an in-depth argument but a couple of points
- I think the MR43T has a tapered seat, the R46N may not
- The R46N is long reach, the MR43T is not, could cause interference maybe?
- I have no idea what the M is

Your chart's a keeper, thanks!

Why did trucks without radios come with resistance wires and plugs I wonder? That's the only reason, to my knowledge, they exist. On Corvettes where they needed extra shielding (no metal body) they only did it on radio equipped cars, so it wouldn't have been unheard of, and a lot of these trucks didn't have a radio.