"A" Body 67 Barracuda rear end problem

Sorry. I have not got an image resizer so I can't post any pics. I will try to describe what has happened here and if I can get any advice on what to do I would appreciate that. Here goes:
I have a 67 Barracuda. the VIN indicates that it was originally a slant 6. The car had a 3 speed manual trans column shift. It now has a 340 V8 and automatic. The 3rd member housing has the numbers 2070741 on the lower left (driver side) of the housing. I took the rear end out of the car because something punched a hole in the bubble shaped portion of the housing behind the "pumpkin" from the inside out. I removed the axles and the 3rd member and found three pieces in the bottom of the housing. The pieces appear to be brass and have the appearance of some type of shear pin about 1/4 inch in diameter. I think whatever these pieces are were picked up by the ring gear and smashed into the back of the housing in several places and penetrating the housing with a semi circular hole. the ring gear has the numbers 2070225 and 3.91-1 stamped on it. This is a sure grip unit. I do not see any evidence that any gear teeth are broken or damaged. I can see that the brass pieces got really chewed up by the gears though. The car has disc brakes on the front. Manual Steering and Manual Brakes. The lug pattern on all four corners is 5 on 4 1/2. The axles appear to have been replaced at some point. I was under the impression that the "A" body cars had a smaller lug pattern but I am not sure of that. I can get no information from the previous owner because he is deceased. If I can weld the hole shut in the housing I would like to rebuild this unit with some higher gears because the engine seems to rev real high when cruising at any speed above 40 or 50 MPH. Any advice on what to do, gear ratios or if welding the housing rather than replacing is a wise thing to do would be appreciated. I have no experience with rear ends or transmissions.