Two big block 440 cam related questions:
(1) The MP 4452783 and the 452927 cam and lifter packages both have the same specs but the latter is a 3 bolt 6 pack replacement. There is almost $100.00 difference in the price of the two cam packages. The 3 bolt is less $$. Why would that be, and does the 6 pack replacement require different lifters??

(2) Are the springs installed on the MP452 heads (115# seat, 280# @ .500 lift, bind @ .740 lift) compatable with either cam above OR with the MP .528 solid lifter cam?

Thanks in advance.