I did a spring over on my truck last spring and I replaced the front shock mounts with the Ford truck ones also. I let the truck extend all the way on jackstands and then added another inch or so to the extended length. I def would make these measurements yourself since every truck is going to be a little different (like mine I took leaves out of each pack). Anyway I ended up just ordering some ProChumps at my 4wheel parts store for like 30 or 40-something bucks each. If I recall I found their sizes online but the people at the stores or online will know this too. Performances wise I guess they work ok, I've never had new shocks on my truck and I've run it without shocks for years also. From some of the reviews and personal experience if your still running stock or somewhat stock leaf springs in your truck you're not going to tell much of a difference if you got triple bypass kings or some $30 twin tube in there like me. If you want I could try and dig up some pictures of when I first put everything together.
Side Note: It sounds like your using the CUCV axles so this might not be a problem but with the stock axles spung over and ford truck front shock mounts the body of the shock (at the axle end) will get smashed by the corner of the U-Bolt plate at full flex. My shocks still seem to work and it didn't puncture them so im still running them.
TBI 454 and chunked up XL's.