Slant 6 Turbo 68Dart Project

I think I made a spark plug mistake, I purchased NGK BP4s, and have been running those based on the fact that most say a NGK BP5 is for a regular engine and works. I see now that the lower the number, the hotter it is - oh boy. I figured one number less meant colder...

So I think I'm going to go to a BP-7Es does this seem right? 2 steps colder than a normal plug?

Also, I'm currently running a "points" distributor that has been converted with Pertronix to an electronic one, and then modified myself for boost applications. Would I be able to piggy back H.E.I. to this or would it be better to just stick to the MSD option?

I ask because a lot of pages online won't really point a direct answer, just to use pertronix OR hei, but they're talking about the full distributor.

I'd like to use the HEI because the '74 dart we just got has the conversion to HEI done already, and the difference is definitly noticable. That car takes minimal time to start and runs real nice.

I got the old ECU box out of it that was not being used, and am going to cut out the electronics and hide an HEI module in there against a heat sink. I think this would look pretty trick, then use a hobbs switch to utilize the 5 degree retard function on it when boost is at 5psi. Someone wrote an article on doing this in Slantsix.org and now I want to do it, except possibly contain the hobbs switch in the unit too, so that a vacuum hose will just go to the "ECU" .

I got a little research in on the Garrett turbo that should come in the mail any day now...

There's a remanufactured unit on a site called xsboosturbochargers that list the Merc turbo as being Garrett part number: 465228

They're rated to 250 HP. I still have not found a compressor map, just a lot of stories on how good a turbo it is, and that it makes power in the low RPM and cuts off about 6k. The other info I've collected is that the wastegate is internally set for 7psi, but people have run them to 24 on other motors. They vary from small Hondas, to Ford pickups, etc... I'll find something eventually. Compressor housing looks like .42 and turbine is .48.