L27 manifolds from 91-92 will not work on an L67. 91-95 L67 or 93-94 L27. And when you get them from a wrecker, they're cracked.
Your choice in dealing with them depends on how long you can afford to not have the car. I know you live close to work, so that helps. Just go on the assumption that all manifolds are cracked with age, so you're either repairing yours or a replacement set. Jerry'* Precision Muffler is the best place here to take them for repair. Jerry has done my whole exhaust, and sponsored WCBF04 for us.
This MUST be fixed before you consider dropping pulley sizes or doing any other performance mods. Welding the outside of the flange and porting the OEM weld on the inside is a good prep step for further mods while you have them off.