the heads i now have are the power pack (pyramid) marking 1965. i've been running the comp magnum 270 with 1.6 roller tips for at least 5 yrs.the impala runs strong with a th 350 ,shift kit and 355 posi especially in the mid rpm range and going through the 3 gears it chirps the tires when shifting from first to second.i was just wondering if 194 heads would let it breath better.isn't that the largest size on a stock bore 283? the carb is a edl 600 cfm on a edl hi rise..thanks for any more ideas !