The kitted A500 with the Magnum motor is a hoot for sure, but one thing I found on the OE Magnum heads was that even though the cracks didn't cause any problems the valves and seats were absolutely trashed.
I could see daylight between some of the valve faces and seats and this motor only had 98K on it.
Lower end looked fantastic.
EQ heads drilled for LA intakes, Hughes springs and retainers with factory rockers, Oregon Cam Grinders mild roller cam, A500 trans with stage 2 kit, headers, LA style accessories with OE V belt drive and a 26" radiator.
25 mpg hiway at 80-85 mph and reliable as can be.
Oh, and it took me three days by myself with no garage and on gravel. :D
