I'm going to be scoping a 336 with either a Leupold fixed 2.5 or VX Hog 1-4. I'm looking for what is the lowest combo base ring set up out there. What would you suggest?

Talleys extra low. Perfect low base for the Leopold 2.5 or a 1X4 as your eye is aligned with the rear scope eye piece perfectly. Most other mounts using Weaver bases are to high
for most low power scopes.

Doc

yep the tallys and a 20mm scope are perfect on a 336. and they are much prettier than a fugly weaver rail mount and don't collect as much junk. i put tallys on all my pumps and levers.

BTDT,,,,, there is no lower mount you can put on a 336 than weaver bases with their old style rings. Period
Those old rings are a little tricky to get just right but once you do they're sturdy as can be.

I like Talley the best but nothing is absolutely lower than the Weaver like Field Grade explained.

Not strictly true. The old one piece Weaver mount with attached rings that allow you to tip the scope off to the side to use iron sights is lower.

I've never seen a set so I'll take your word for it but they couldn't be much lower without interfering with the hammer.

I like the Weaver #63B on my Marlin 336s. I have cut a couple of them short, one of Marshall Stanton's better ideas, so that I could install a Lyman 66LA peep sight as an auxiliary sight, using low Warne Maxima QRs.