I rarely see posts about these but my '54 gmc has a bendix frame mounted booster that the PO added. This truck has amazing power brakes like you have to tell anyone driving it to be careful so they don't crack their head on the windshield. The PO also uses this setup on a 48 and a 51 chev 1 1/2 ton dumptruck that have run daily for 30 years in his business. I should ask him what they are and where he gets them. No clearance issues on the firewall and man do those things stop...... I'm spending the day with him on Wednesday going on a long trip to pick up another ch**vy for him so we will have time to discuss his power brake setup. I'll report back on Thursday