I dunno anything about megamod. But I suggest you use Killap Bear Dude's mods/patches.
Killap suggested on the NMA-forum that this megamod does not contain the newest version of his patch but rather an older one. So I prefer his mod.
Unofficial FO2 patch: http://www.killap.net/fallout2/patches/unofficialFO2patch.exe
&
F2 Restoration Project: http://www.killap.net/fallout2/expansion/1.2/F2_Restoration_Project_1.2.exe
I recently restarted FO2 and this mod works like a charm.
Only problems I'm having so far is Farrel's garden quest (known issue) and the ammo damage formula but I can set this back to the Fallout default in the ddraw.ini file. Now I'm heading off to New Reno in my brand new car. I finished Klamath, The Den, Redding, Modoc, Vault City and Gecko. So far except what I mentioned no major glitches.
Good luck...