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Discussion Starter #1
Im pretty sure my front springs are original. They measure .670 rod dia.

I plan on doing the 1” Shelby drop and running 17” rims all around.

I have a 302 going in with aluminum heads and intake So there’s a fair amount of weight reduction. I have ordered full roller perches from open tracker.

Im not entirely sure which springs to get? There’s a lot of references to a “GT” spring but I’m only finding springs for engine size and with or without A/C.

I am looking for a better handling front end, so likely a stiffer spring. What’s the stock spring weight?
 

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Im pretty sure my front springs are original. They measure .670 rod dia.

I plan on doing the 1” Shelby drop and running 17” rims all around.

I have a 302 going in with aluminum heads and intake So there’s a fair amount of weight reduction. I have ordered full roller perches from open tracker.

Im not entirely sure which springs to get? There’s a lot of references to a “GT” spring but I’m only finding springs for engine size and with or without A/C.

I am looking for a better handling front end, so likely a stiffer spring. What’s the stock spring weight?
Those sound like very big springs and am thinking they're aftermarket. I believe the measurement of the coil, in your case a .670, is probably like what most call a 620lb coil spring and would have to assume they're aftermarket. They might even be 1" lowering springs. If the springs are in decent shape, why not just re-use them? If your ride height is too high you can always cut 1/4 to 1/2 of a coil off to get the ride height where you want it. If the springs are still decent, I'd re-use them. And when you say you're looking for a better handling front end, what do you have on the car now? Better shocks, thicker Monte Carlo, export braces, sway bars as well as a stouter crossmember are going to help you out as well.
 

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Since you're not calling your car a GTA I'll just guess it is/was an original manual trans. (It makes a difference.) Also need to know if it originally had A/C or power steering or both. The 302 4V, Fastback, and GT option group info I have already.

There was no .670" wire diameter spring for mustangs in '68, though there was a .675" one. That spring would have been for a standard Non-GT spec car though. It was rather long at 18 1/2" free length and 9 3/4 total coils.

But most likely your car came with C7ZZ-5310-AG springs, Spring Code 4S. That spring had a .625 wire diameter, 8 3/4 coil count, 15" free length, and a normal total load of 1,580 lbs. Not sure of the exact spring rate, but that was the factory spec for a 1968 J Code fastback GT with no or only A/C, no or only Power Steering. If your car had both A/C and PS the spec was Spring Code 4R, 1/4" longer to increase the total load capability. Only very slightly different.
 

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Discussion Starter #4
So the car IS a GTA.... came with C4, A/C and power steering. I'm converting it to a T-5 and will keep the AC and power steering.

To be honest the caliper read .673 ish... I just rounded down.
 

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So the car IS a GTA.... came with C4, A/C and power steering. To be honest the caliper read .673 ish... I just rounded down.
In that case newish VMF member @ElConductor surmised correctly that your current springs were not original to your car. The spec for a '68 302 FB GTA with both A/C and PS was the aforementioned Spring Code 4S. :)
 

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Discussion Starter #6
OK thanks for all the info guys. So, I'll pull the springs this weekend and do some measuring to be sure. Of course, I'd be more than happy not having to buy new springs... ;-)
 
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