Whats your garage ceiling doing for you?
I recently installed a pull up bar for a friend as a Christmas present. The install was quick and easy as the drywall was not painted allowing the tape lines to be visible over the studs. I reconfirmed the center of the studs with my stud finder and installed the standard size Stud Bar in 20 minutes. Having a helper on the ground handing you tools and screws is crucial, saving you many multiple trips up and down the ladder. I highly recommend it. The before and after photos are below: