masive huge gigantic large big oil leak

[stresscrack]

hey guys. been lurking around your site for a while now. I have an issue so I signed up and hopefully someone can give me some advice.
I have an 123 diesel I did the 4 speed swap. and unfortunately I didn't do
the swap my self. so I wasn't there to see what all went on. I had a redneck buddy of mine do it. hes pretty handy as he builds all of the guys custom mud trucks and such. anyway after some back and forth figuring out the shifter, bleeding the master and stuff we got it going and its pretty cool. but in the process the car has developed a HUGE oil leak. like blasting windshields behind me oil leak. oil is pooling in the bell housing but I'm not sure where its originating from. (its not the valve cover) 6 or 7 qts in 45 miles back from his place. any ideas where I should start? rear main? saw a vid on the oil cooler housing, maybe? please any advice would be great.

thanks guys