Old school Zalman Reserator 1 HELP PLEASE

So here is the situation, I really need help from those who have done more liquid cooling than I have.
What Im doing is building a throwback athlong 64 system from when I was in high school and going to lan parties.

Heres what ive got-

Motherboard will be an A8N-SLI running a 4200+ dual core

The cooler I have is an old Reserator 1, I need to do a few things but what I have currently is the tower, PCI slot pass through fittings (These are important as I want to use a case that was "pre watercooling" so no fancy ports for tubes
and I have the original cpu waterblock and mount.

Id like to re-use as is if possible, but what im struggling to figure out is the tubing, it seems to me that what was used inside the case is most likely 3/8 x 1/2 but it seems the stock tubing on the tower side might be smaller than that?

Any advice? I just want some simple clear tubing as I will most likely use a colored/UV fluid additive, whos got a decent protection for mixed metal these days? was just going to go distilled with an additive because i dont wanna pay 30-40 bucks a bottle for fluid, this is kinda a big system

manual says 8 or 10mm tubing only
can just use rad fluid and distilled water. a 10/90 mix it about what they use in aios. its all ive used for years.

So 5/16 x 3/8? im admitting im dumb here

yeah something like that. i dont know the conversion off the top of my head.