Is it ok to / any draw backs to switching out a set of solid roller lifters? I know the flat tappet lifters need to stay matched up to their lobes if pulled. But ordered a spare set of solid roller lifters, thinking about putting the new set in for the rest of the season and sending set that's in the motor in for a check up over winter. Need to do a valve lash check before making the decision. . . but wanted to ask the masses before I do.

Swap them. Because of the roller itself they do not develop a wear pattern on the camshaft like flat tappet lifters do. I don't know how old your current lifters are, or what spring pressures you run, but the roller will fail after time. Then it trashes ehe camshaft itself.

Yea, I need to get into this area because having oil leak issues with the valley pan. Adding a vacuum pump, and need to reseal the valley pan. But since I'm tearing down this far, I thought I'd swap lifters since I'm here. They were used, suppposedly not much, but I wasn't sure how much. So since I put the new motor together it's been on the back of my mind that those could cause me trouble and since I'm that close. . .might as well swap them.

Solid roller lifters can vary on quality from one brand to the next and what application they are for.
A " drag race" lifter versus a street and strip lifter can vary a bunch from one brand from a cam company to another company lifters
Another variable is the diameter of the roller wheel and if is bushed or has needle bearing in it
Bottom line is you can probably send your old lifters in for a rebuild and then know exactly how many miles or races get put on them while you own them

If there comp cams lifters they don't rebuild them any more.

and here comes the "stoopid old geezer" question of the day...........
do the high horse power [700-1000] late model hemi factory lifters need rebuilt as regular maintenance, and if not, why not ?

They are hydraulic instead of solid and don't take a beating like solids. That said, some still fail.

thank you sir !
i know they are hydraulics, but i wasn't sure if the spring loads used on them would require periodic rebuilding, although not as much, like the solids would.
again, thanks for putting up with my "stoopid" questions.........

i use the Crower Ultra lifters for my race motor builds with .820 diameter wheels