If budget is key then stick with the 068 cam which will play nice with your press-in studs more so than anything else, but that means sticking with the original 1.5:1 rockers.
You’ll probably be floored when you see the machine shop bill to tap 16 holes for 1/2-13 (its either that or 7/16-14 Heli-Coils) and the cost of the conversion studs with 1/2-13 bottom threads (around $100) or just the normal kind that are 7/16-14 bottom threads ($65). Plus they’re going to charge you to pull the old press-in studs out.
I once converted a set of #66 455 heads to screw-in. I made a tapping block to guide the tap in straight that I could bolt down using the old stud adjacent to the one I was tapping 1/2-13. After pulling the first press-in stud using a stack of washers and an old rocker nut and tapping that hole I used a 1/2-13 bolt to hold the tapping block in place and pulled the stud next to it and tapped it, repeating until all the holes were tapped.
It was a bitch to do by hand, plus I needed another bottom tap along with a regular tap. Then I had to grind about 1/8” off all the studs and deburr them because they’re a bit too long, otherwise they would bottom out before they could be tightened. It’s easy to see why shops charge as much as they do when you start to understand what all goes into it.
And yes the studs went in straight and didn’t look like a bunch of old trees in a forest.
