I might have what your looking for. If my memory serves me correct there are different types for different style bands i'll dig around and see what i got
. I believe we used a dist. From a 87 Ram for our street stock that does not have the cover plate. This is not a lean burn system but a early computer system.
904 and 998 are basically the same trans 998 has lower 1st and 2nd gears and more clutches you may want to get the torque converter from the 76 should be non lock up your 87 may be a lock up you should be able to use your 87 driveshaft transmissions should be the same length
I would say your problem is as said in earlier post they used exhaust valves that originally had rotators on them we had this same problem with our j heads we had built just had to get valves and keeps for non rotator exhaust valves problem solved