I have a 1970 GTX with a rebuilt/original 440/375 hp motor.
I have TTI Headers and a Hughes Cam....nothing too eratic or irrational. I don't race the car...I just want it to be the best that it can be.
I would like to tune this car up ...for the first time that I have it.
I also have an MSD Distributor.
What kind of spark plugs should I use? NGK,Autolite,Champion??? and what's the gap?
I don't mind spending extra $$$....I just dont want to do it again for a very long time...
Also want to change the Cap, Rotor and Wires....any thoughts?

I like Autolite 85p (platinum), others like NGK's. I've had enough Champions crumble upon removal to never buy that brand again.

Stock gap is.035. If you have a hot coil, and the control box to handle it you can go up to .045, but gains are minimal on a mild street engine.

Dial in the dist adv curve in order: initial/total/springs/vac adv. brown cap with brass inserts (see Joesixpack a member here). Firecore plug wires get regular rave reviews. Check rotor phasing. NAPA Echlin "MO3000" rotor with a .060" longer blade $8 & change out the door. Experiment with gaps from .030 to .045. NGK or autolite overseas now & the quality ain't the same as it was. 180 or 185 stat. Is that just a MSD dist or is it the regular MSD multispark system. What coil. EDIT If that is an OE AVS (& I'm assuming that it is) then it is without a doubt LEAN & I would convert to Eddy 2 step rods/short pri jets. Get a performer strip kit with rods/jets close to what you have in there and I'd go maybe 3 thou thinner (richer) on the cruise step for a start. From a prior thread: the '70 AVS has a .101 pri jet and a .066/.058 rod and no mention of the "intermediate" dia as (OE) AVS's are 3 step rods with the taller (pri) jets. Mike yours & go from there & can likely google the part number for the diameters if you ain't got no mike. Holler how thing turn out.

Sounds like a very cool car. The Firecore50 Wires will fit out of the box, perfectly. All numbered and ready to go. Any pics of your car and engine? Sounds killer.

Hah! NGK plugs have always been made overseas, same as Nippondensos. As one of those companies made the Accel U-groove plugs, them too.

Plug gaps - the larger the gap, the larger the flame "kernel" that starts everything off. There's a reason GM went to huge gaps in the early HEI days. I have taken a set of overused plugs out that had gaps of 0.060, measured. Putting new plugs in, gapped at the factory 0.045, I thought I'd see immediate mileage increase, but not even a tenth of a mpg.

The larger gaps stress the plugwire insulation more, so they don't work if your wires break down before the spark jumps. The spark will go somewhere, that's for sure.

I've used lots of plugs, Autolites seem to work well, Champions did too but tended to foul faster, I don't know why. But lots of races have been won with Champions. I've used Bosch Platinums, had some failures. I've used AC plugs, they don't seem to get much play around here, but they've been very good for me. Maybe because they're from (gasp) GM? But they worked reliably for quite a while.

R.

HELLO I RUN AUTOLITE 86 IN ALL OF MY BIG BLOCKS AND THE ACCEL 300+ PLUG WIRES .NEVER NO TROBLE WITH THEM .STOCK CAP AND ROTOR . A REAL MOPAR MAN

How old is that MSD distributor? On a mild engine, we would often get well over 50,000 miles on caps and rotors. Especially if the cap had brass posts. Unless there are carbon tracking or other issues, they are not much of a wear item in normal driving circumstances.

Are the MSD cap terminals made of brass or aluminum? Brass is the only way to go, if available.

Champions or Autolites will be fine at .035 gap.

FireCore wires are the way to go.

If you want to go to the trouble, what RapidRobert suggests will be well worth the effort. Those adjustments are needed with today's excuse for gasoline.