I would re-use your original lifters , if possible. New hydraulic lifters kill rebuilt engines so frequently that some builders have given up. I personally know two engines that were destroyed by new hydraulic lifters failing in rebuilt engines during the run-in period. Both went with roller cams after the catastrophic failure of their new engines caused by the failure of the hydraulic lifters.
Re-grind the old ones and get a new Melling cam.
