Start with a bigger motor. You'll have to use a 4-speed, or a big converter to get good performance out of the 327.

I've run a number of 327s, all of them "tweaked", but in a car as heavy as yours, I'd go for a 400 smallblock, or quit messin' around, and build a 454. The '65 was avilable with a 396, so the parts are available to go bigblock. I doubt if it will cost much more than buying your engine one piece at a time.