Couple of things tho since I have never done a conversion.

1. I dont know if the early block has tall enough lifter bores to deal with the hyd roller OEM style and the oiling it needs.

2. I think that you may need to use a retrofit cam in the block that has a smaller base circle.

I am not POSITIVE on either of these but do consider them.

Now if it is NOT an OEM style hyd roller cam but it is a hyd roller cam (or solid roller) then you can pretty much just junk the stock spiders retainers and taping the lifter valley as the new rollers will handle this.

Also you may need shorter push rods for either roller lifter application (OEM) or aftermarket.

Another thing to remember is that you will have to have new springs put on the heads to handle the roller cam.......either one OEM or aftermarket to realize the full potential of the roller cam.

Just get the specs on the cam.

I change the springs when using ANY cam with over 500 lift or more than 230 degrees of duration at ANY lift on STOCK heads/GT-40 heads.