I used used the engine systems set. my machinist was busy for a while with them.. They are double registered where the ones in the pic appear to be single. the ES ones are a pretty tedious install according to my guy. They are beefy. He took them around the shop and ask people to guess what they were for. Based on the sheer size of them , most said a top fuel or prostock type deal. There are heavy. Think I paid just over $400.
The caps that Engine Systems sell are Blue Thunder caps. I have installed two sets of these and they fit really well. They are tedious to put on because you have to be so careful, but they sure are nice when finished. There is a dealer on the forum that sells BT caps. You might get a better deal thru him than ES.
That's what scared me off of them. I seen them on e-bay, and since they're made in Canada, I thought they might be a good deal, but something didn't look right. After a few minutes of staring at them it dawned on me that #3 looked just like #2 and #4.
They are probably machined the right thickness....
and don't need to be machined any more. But, that might mean the rest of the cap is thinner than it should be. Also, look at the chamfer on the caps. If the final bore size will remove the chamfer, ok. If not, that's less support for the bearing.