Maybe those Z06 heads have bigger chambers then the little 325" heads and you have effectively dropped your compression down some. Unless you milled em to keep the same CC. Z06s have different pistons and larger bore, both adding compression, thats why they use larger cc chambers to keep it at a streetable CR level. I bet most of your problem is in the convertor not letting you access your big power which is way up there, that explains your low 1/8 mph. In the 1/4 I bet you fly on the big end. Hell I have gone 74mph in the 1/8 twice and thats with only a few bolt ons and in 95 degree heat. I bet you go 78-80mph in the 1/8 easy once you get it to leave and get the gearing straightened out. On my 78 TA, it leaves pretty well and goes 88-89mph in the 1/8, but in the full 1/4 it would only go 108-109mph. Thats only picking up 20 mph on the back half. It was setup to leave hard. It would do 1.58-1.60 60's. This was with a loose 3500 convertor, 3.42 rear and 406" pontiac. Its all about getting it out of the hole!