Well I was shitting around in Hammer today found that L4D maps do work in GMod with proper tweaking. I've fixed a few problems in the map, and theres on major one. L4D relies on alot of film effects that are incorporated into the new engine, GMod's EP2 engine doesn't have it.
Since models have already been ripped, it was quite easy to get it working. Some things gave me trouble, but I suspect that we will have fully working GMod maps sometime in the future. Oh, and the appartment below is missing things like holes in the wall because I patched it for a comic I'm making (In case you're woundering).
I would of taken more pictures but then the damn rain crashed me. Gotta remove that next compile
Rejoice guys, we've almost got them.