MH merged this with the original E2M6 map a while ago already. You can download it here (even with LIT file for colored lighting): http://www.mediafire.com/download/b6oocqconu70zxv/e2m6-full.zip - I am rating this as a part of the merged release, and as such, it is fantastic. The ending of E2M5 finally makes a lot more sense since it ends in a cave which is logically continued here. It's maybe about 2-3 minutes of additional gameplay compared to what you know from the original map already, but once you have played it, you won't want go back to the version that was released back in 1996. Thanks a lot to John Romero for making this available, and thanks to the Quake comm for using this material to recreate E2M6 John wanted it to be played!

Thanks for merging, but how can I start wuthout any weapon?

Play up to E2M5 normally, take a note of what health, armor, weapons and ammo you ended with

Enter the console (` button) Type SV_CHEATS 1 Restart game by typing MAP E2M6 Enter console again Type GIVE 2, then GIVE 3 and so on until you have all the weapons you had at the end of E2M5 Type GIVE SHELLS 100 (or however many you had) Same for NAILS, ROCKETS, CELLS, HEALTH and ARMOR.

This has been repurposed in (https://www.quaddicted.com/reviews/contract.html "Contract Revoked").

(one day I'll remember how Markdown works here)