1969 c10 454 swap header problems

[Poser33]

So I have a 1969 c10 and have just swapped out the old 350 for a 1973 454 I'm running the performance online motor mounts and can not find a set of headers to fit I currently have the Sanderson bb8 and the driver side hits the mount and the block and the passenger side I can't even get close to bolting it up because it hits the frame bad any ideas thanks

[El Dorado Jim]

may have to use stock exhaust manifolds

[68is4me]

Not sure what "performance online motor mounts" are but I am running the bb8 and mine fit fine. I am also using stock mounts in the stock locations on a 68. The only mod I had to do was shave a little material of the 700r4 to fit. So my guess would be the mounts are causing the issue.

[Poser33]

On the passengers side the header is hitting the frame and hitting the corner of the th 400 it might clear the frame but I would have to cut a lot off the transmission
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[68is4me]

Couldn't find a pic of the pass side but found a couple of the drivers side maybe it will help.

[Hypertrophy]

Which engine mounts are you using? Going to do the exact swap in a 1968 GMC and want my headers fitting!

I searched PerformanceOnline and do not see the BIG BLOCK Frame Stand and Motor Mounts that supposedly allow for header clearance, so that may be your issue...

[Poser33]

I have the performance online tube motor stands and have tryed several headers and just tryed headman mid length headers and the passenger side fit but the drivers side hits the frame and the mounts bad, I have to raise the motor up almost an inch to clear the frame it seams like the motor is sitting to low in the frame, how far above the crossmember should it be to the crank pulley thanks

[wbc409]

If I remember correctly, factory big block trucks had a slightly different shape to the front of the frame. The frame rails had a slight cut out, or trimming at the top and bottom edges for exhaust clearance.

I put a 454 and th700 into a 71 c-10. I used the square body style clam shell mounts. It was super close on the front passenger tube to mount clearance, but I didn't have any issues with the tranny. I used Hedman full length headers. Didn't like the way they hung below the frame, but they have been on the truck for years with few leaks.

[Hypertrophy]

This is what I have read and been told to use - Big Block Motor Frame Mounts to ensure the headers will not have any clearance issues. I have read on other sites where some people have had clearance issues with the tubular mounts, not all, but some. . .I'm not chancing it. I'm using the ones in this picture.