if you absolutely need to build a mesa mark series, there are a couple vero projects you could try:
(although these are lead channel only - do you know which channels Trey uses? there's not a lot out there for the rhythm channels).
Based on a schematic of the Mesa Boogie Mark IV I found floating around the Internet and the owner’s manual I put together a schematic
sabrotone.com
dirtboxlayouts.blogspot.com
alternatively, if you would like to build something from the PedalPCB library - tbh, just about any high gain style distortion / preamp will probably get you close enough.
the amp is just one piece of the tone puzzle - we're not taking into account whatever other devices are in front of the amp, in the loop, and then there's the speakers/cabinets, which probably make a bigger difference than the choice of amp.
high gain possibilities:
Compare to Wampler Triple Wreck
www.pedalpcb.com
Triple Rectifier. (Wampler Triple Wreck) - haven't tried it. supposedly pretty good , its opamp-based, so I'd be confident it's a winner.
I guess it's somewhat Mesa-adjacent at least.
Pathogen Distortion (Abasi Pathos) - supposedly a couple values away from being a Wampler Triple Wreck clone lol -
Compare to Abasi Pathos
www.pedalpcb.com
other high gain suggestions:
Compare to Steel Panther Pussy Melter
www.pedalpcb.com
(ive actually built this one and it's the best distortion ive tried so far)
Compare to Revv G3 Preamp/Overdrive
www.pedalpcb.com
(highly rate this one too)
Compare to Victory V1 The Kraken
www.pedalpcb.com
Compare to Diezel VH4
www.pedalpcb.com
Inspired by the Friedman BE-OD, the Thermionic Distortion provides searing British-flavored high gain tones through any amp. Pedalboard friendly design, 125B footprint with top-mounted jacks.
www.pedalpcb.com
i wouldn't recommend the Dr Boogie, it's so heavily mid scooped that it's barely useable (to me at least)
probably the best way to decide is to check out some youtube demos and have a listen to the options you're considering...