Long shot I know (recently replaced one of the vertical bolts in my rear mounts and it's a tight area) but perhaps a 90 deg. offset 3/8ths drill, either air or electric and a short drill bit?
RonR
1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1964 CJ5
| 
