[JLMounce]

When I first did the top-end on my engine back in 2015, like you I tried using the factory pan. I installed it dry and rotated the engine over several times to create any witness marks. I had a couple, so I used a ballpeen hammer to clearance those areas. I figured based off of that and the addition of a gasket I was going to be in the clear.

Almost immediately I had leaks all over from the valley pan. No real clattering that I was hearing, but the engine was noisy anyhow. I ended up replacing the factory piece with the tomahawk valley pan. I tried a couple times on my end to get that to seal up, but had trouble with it weeping oil out of the back on top of the rear ledge of the block near the distributor.

I think it may have been Steve C that had a write up, that I followed on getting valley pans to seal that finally squared me away.

I used a gasket as well, but I believe his instructions were to only use RTV.

Use only enough RTV to evenly coat the sealing surfaces, without creating a lot of bulge that may find it's way into the engine.
Use RTV on the under side of the stud bolts in the center of the pan.
With the RTV still wet, place the pan on valley and make sure it's not hanging up on the ledges found on some heads.
With only mild pressure on the pan, let it sit and cure for 24 hours.
Once the RTV has cured, tighten down the pan to spec. It's only 42 inch pounds, so it's not a lot of force. Over-tightening this will cause leaks as the pan is pulled out of square with the block.

That's what worked for me and after I started using that method, I never had leaks from that part of the engine again.

In regards to what lifter is going to be the best for you, since you have the engine apart and can measure, I'd follow what Butler is providing here and purchase the lifter with the oil band height that best matches your block.

https://butlerperformance.com/n-1349...formation.html

I believe they state that the Comp Evolution lifter has the best oil band height for most applications.

I ran the non-update Morel lifters (Lunati brand) for about 8 years and although they were noisy, they didn't give me any reliability or performance issues. I'm running the short travel version of the Johnson lifters you have currently and so far they are working out great. They are quite, even with a .399" lobe lift cam and they easily handle my engine's 6000rpm shift point. I haven't had any hint of valve float from them. They are set up with HS 1.5:1 rockers and PAC 1903 valve springs.