Sometimes brackets need to be spread a bit to get the new poly bushings in, and a hammer is also helpful. Grease the bolts for corrosion protection, and, after aligning the hole and bushing with a drift punch, slide the bolt in. Install the nut on the bolt, but leave it loose until everything is assembled in case the components are slightly misaligned. However, don't forget to tighten the nuts after installation is complete. On some vehicles with headers, the bolt may have to be inserted from the backside.