well good advice! :D

now I need another 7.5 motor

Which one were you using, the bank of 5 or the bank of 2??

while I was melting plugs I had the row of 4. Now I have the bank of 2 which came with the speedo

I use both (row of 4 in 2wd and pack of 2 in 4wd), choice mainly down to what fits but I'll watch out for that one.

Was it a capacitor that failed or something else?

no idea. I just know it hasn't happened since touch wood!