Differences with Ram Air III D-port repo manifolds
 

I would like to install Ram Air III D-port manifolds in my '78 TA. There appear to be three different offerings:
1) 1968 to 1972 GTO
2) 1964 to 1967 GTO
3) 1970 Firebird
The only difference I can see is usage of a two bolt/ three bolt collectors on 1) and 3) and two three bolt collectors on 2). Is there a reason why 1) or 3) is chosen over 2)? I bought a Pypes kit with two 2.5 inch flanges.

Ram Air III D-port manifolds with machined 2.45" collectors seen to be scarce. eBay has some but the also charge me sales tax..

the 67 have 2.25'' outlet and 3 bolt flanges, rest is cosmetic differences and accuracy between year and model

Your number 1 and 3 have the same part number at Year One.

Clay

The 64-7 GTO factory headers tuck in a little tighter to the block.
 

The frame on the earlier A-body cars is narrower around the engine, so the headers fit a little closer to the block.

One thing that would do is put the heat radiating off them a little closer to your starter motor.

Everyone says they will also fit the later models, but we've never actually tried that.

Having three-bolt flanges on both sides is a plus.

Good luck!

The outlets were in slightly different position between the '67 GTO HO manifolds & the '68 GTO HO manifolds. Twenty plus years ago RARE's left hand A-body/2nd Gen Dport manifold was patterned off a '67. Know I had a friend that had issues with fitting just such a manifold on a '70 4spd T/A. That issue was addressed by RARE with more correct Dport manifolds being offered for '68-70 A-boys.

On a true '70 RAIII restoration, I've sought out original '70 RA III manifolds in great shape. Which manifolds, it all comes down to what ones building or restoring.

This is correct. I had clutch linkage clearance issues when I installed reproduction '67 A-car manifolds on my '76 T/A. I remember being disappointed and perplexed when I'd believed they'd install without issue. I'm glad to hear that RARE does offer the correct outlet for 68-70 A-body and 70-up F-car.

Certainly the manifolds are worth doing, but there are wiring and heat shield issues to keep in mind as you go along. Without addressing them, the wiring will likely be fried and look like what I found when I began to experience sluggish starting in my GTO, even after putting in a new battery.

First, there definitely is a different solenoid heat shield for the starter. The RA version is significantly larger and provides much more protection.

Second is the starter portion of the wiring harness. I'm not sure how the TA arrangement works, but with the non-RA GTO installation, the wiring to the starter usually passes either through a tube between the #s 5 & 7 cylinder portion of the original log manifolds, or it comes in from the back of the block along the oil pan. The previous owner of my '70 GTO did the same conversion and neglected both. The attachments show what I found and needed to do to correct the problem.

Basically, I had to extend the starter wiring as it would have been in the RA version of the engine harness. It goes forward from the firewall along the valve cover / intake manifold valley towards the alternator, where it then it drops down the front of the block towards the fuel pump. Once there (at least on my GTO), it meets up with the starter cable and they are routed to the starter along the oil pan rail, suspended in the open air from clips. They pass behind the motor mount and emerge at the solenoid, from a direction opposite the radiated heat from the manifolds. Once I made those repairs, I've not had a single starter/starting issue. Hope this helps.

FWIW, the outlet to the down pipe is further towards the rear of the car on the 67 manifolds. The 67 GTO dirt car in my second signature picture has 1970 Judge RA III manifolds on it, because rules stated you had to use cast exhaust manifolds in that class.

I had to do some creative surgery on the crossmember that is under the engine to make them fit because the later manifolds have the down pipe connection further towards the front of the car. Without cutting into the crossmember and removing some of it, there is no way they'd work on an earlier chassis.

I would never attempt to make them fit on a nice car, the clearance modification was done with a cutting torch. Stock cars don't have to be pretty, they just need to be functional. It worked, and the car was faster with the RA III manifolds.

I have no recollection of how I wired the battery cable etc, I'm sure it wasn't pretty, but it didn't have to be. The pipes from the manifolds rearward were made from driveshaft tube welded to the original stubs of flanges and the flared OEM pipes. Again, not pretty, but low buck, low restriction, and functional.

Later on we used those same manifolds on a 72 Firebird chassis for another dirt car, and they fit fine, with no modifications.

I still have the manifolds on a shelf in the garage, 44 years after I put them on the 67 GTO (1976).

I've installed 67 style into a 71 gto. I did have to do some very minor grinding to get some clearance for one of the 3 bolts. I also used an allen head bolt to make tightening it easier. If I remember correctly the grinding was on the exhaust flange.