Which heads wpuld be better?

Yep, They put more material in the ports to help with this problem of cracking, so yes they'er better than the old stock stuff.(Magnums production)
Although $300.00 isn't a bad price either if they'er truely rebuilt heads. Check the guides and the springs as this is a problem with magnums. I've had to replace many a spring and guide, seems they know this as they sell springs 1 at a time.



BJR Racing