Join Date: Mar 2002
Location: Austin, TX, USA
How much are you off? Is it an 1/8" or more like a few thousands? Are bushings aluminum? What I'm thinking is that if you're a few thousands shy, they should seat properly once torque and weight is applied. Otherwise, sounds like you'll have to get a die grinder or dremal tool and carve it out a tad from below.
Those 5/8" holes are handy for lining things up in a couple of ways. One, you can stick a drift in there and manuver the frame around. Second, once you're ready to torque you can install a 5/8" alignment dowell in there to get things lined up perfect. A piece of 1/2" copper pipe works pretty good. Then again, my front end is stripped. With the front end assembled, you may find the copper pipe is good for alignment but not adjustement (i.e. it will bend if you try to move the frame with it in the holes).
There are also holes in the rear subframe near the spring shackles. There are a couple holes on the inside of the front subframe near the cross member. Lastly there is a hole dead center on top of the large K-member. Between these 5 other holes you can get a pretty good alignment by taking cross measurements with a tape measure. Just remember that it is probably more important to get the body work lined up that it is to be perfectly square. The factory may not have done a very precice job.
As for slop, there is quite a bit of slop in the frame mounts. You can probably slide it in any direction by as much as a 1/2", so you should haven't any problems...unless the solid bushings have 1/2" holes in them. I don't use solid.
If the front end of the car is installed while you're replacing mounts, just be careful with the fender alignment and such. Sometimes when you get your mind on a big rigging job like that you can loose focus on little things that ruin your day.
Get the alignment close and snug the bolts. Let the car down slowly and make sure nothing gets bent - like the fenders. Torque the bolts to spec once the car is back on the ground. This will also give you a chance to tweak the alignment (like doorgaps).
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI