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Discussion Starter #1
I recently noticed I have a wheelbase issue with my car. I’ve been swapping to a new Mustang II based subframe for a while now. I just noticed some shims in the floor of the garage where I had took the original subframe off that I’m pretty sure were on the lower subframe between the subframe and firewall support braces but between starting and stopping this project I had forgot the shims..

Now here’s where the issue is. The wheelbase is off by around a 1/2” on the drivers side 109.5” compared to the passenger side which is 110”. I have noticed past crash damage on the car nothing bad but noticeable on the firewall floor bracing on the driverside but it doesn’t look like there would be a 1/2” difference.

The clip is assembled with the wheels on a the engine in the car.

Im trying to figure out where my issues are coming from. The measurements I’ve been taking off the new front clip seem to be good.

I found a link to a Fisher body manual that may be of some help tonight. Feel like 1step forward and two steps back all the time with this car.

Anybody ran into a similar issue?
 

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I noticed My 67 is 3/8” longer wheelbase on the passenger side after the TCI front clip install. I never measured it with the stock suspension. I discussed this issue with my alignment guy and he said that it’s not uncommon at all. The car tracks straight and drives fine.
 

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Discussion Starter #3
Hey thanks glad to hear yours worked out. Im like you I never measured it with the stock suspension so I don’t know what it was like before.

Im starting to think the lower firewall/subframe mount area on the driverside is pushed back. May try to get out tomorrow and take some measurements if there’s any I can compare to from the Fisher body manual. If it looks like the firewall is pushed back maybe I’ll make a shim plate to get the wheelbase length right.
 

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You might want to check your fender to door gap to see if the 1/2” adjustment is possible.
 

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Discussion Starter #5
Yea your right, probably don’t have that much play.
 

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You might be alright. As I mentioned, my alignment guy who specializes in classics and hot rods says he sees this quite often.
 

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Discussion Starter #7
That’s true. I was just determined to figure out what I had going on. I just found a pic I had taken with shims in between the old subframe and firewall. The shims only measure around a 1/4” so I’m just guessing the old clip still had the wheelbase off by a little.
 

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a difference in wheelbase could be caused by numerous things, the rear end could be off, if the rear end is off by 1/4 on one side it will make 1/2 inch diff in wheelbase,bad suspension parts, the caster will affect the wheelbase. x measue the underbody to determine if its square.
 

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GM doesn't mention anything about the shims you are showing, just the ones at the top. Probably got pushed back just a bit and got a bandaid somewhere along the line. As mentioned above, if your fenders line up that doesn't look like it would cause a problem.
 
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