My brother has an 84 short bed s 10. he runs a n/a 383 w/ t350. Problem is we keep breaking transmissions at the bell housing. first trans was at the track at 1000 ft mark spun trans sideways in truck. second was on the street. We run solid eng mounts and polly trans. Is this a bad thing? should we have all same mounts? Im starting to think its the cage. We have an 8 point all inside the cab, w/ no bars going out into the bed. making frame flex? Any other ideas? thanks for your help. joey...