+1 on staying with the 292 . Unless you plan on changing the gearing there's not much to be gained imo . You'll get from 0 to 50 faster , but that's just about all its going to do .
The torque of that six is unreal . And keep in mind that the 292 is almost a 300 cid engine . Not a racer , but it'd climb a cliff . Guess it all depends on what you are looking for . Your truck .
If you're going to scrap that 6 , please give me a shout .
Not sure about the frame mounts , but one of the major parts suppliers that can be found in any good size town, had a book full of different styles of motor mounts . I was really surprised at the amount of motor mounts available . There were some frame mounts as well .