Another big block tower question

[Radford46]

I’ve got a 68 c10. It came with the 250 inline 6. I’m converting it to a 396. I bought new, after market, bb towers a couple years ago when I started gathering parts. After some set backs in getting started, I started fitting them and they don’t fit. (And I cant remember where I got them!)
The bottom hole when lined up makes the top 2 ‘pop up’ about an inch from the frame holes and it seems like the frame needs to be trimmed about 1/4” from the inside edge to accommodate the brackets.
Well, I figured the aftermarket ones were off,Since everyone claims aftermarket stuff sucks, so I invested even more money in a pair of the originals. Same freakin fit!
Does the frame need to be trimmed some? I’ve never seen that mentioned, but I’m wondering.
A little help?

[richard2717]

Do the stands look like this with the big center hole? Are you trying to mount them back where the 6cyl stands were? Here is a picture of them in a 68 suburban I parted but it does look like the frame was cut back. Have no idea if it is original or not

.

[Radford46]

No, I’m trying in the two forward holes as I’ve been reading about. But it definitely has been notched. I was of the understanding that all the frames were the same, but maybe not?
But those are the same stands,

[Radford46]

I meant that yours look like it’s been notched probably factory.

[richard2717]

I have several here that I just went and looked at.

68 suburban original BB frame notched both sides back to 1.75"
(3) 67 pickups and none are notched
(2) 72 small block pickups both are notched
my 68 panel that was originally 6 cyl but now small block is not notched
(2) 72 suburbans One BB one SB both notched


So it looks like somewhere between 69 & 71 they started notching them all at least on the 2wd

[Radford46]

That helps! Thanks man.

[richard2717]

to add...... I forgot I had a 69 suburban frame sitting here so I just went and looked at it. It was factory small block 2wd and the frame is notched on it so I would say 69 was the change year

Edit to add pics of the 68 frame without the stands in the way

.

[68Gold/white]

My educated guess on the frame width, from info here. 67's all had upper wide frame width. 68 being first year for big blocks, the big blocks got the 1-3/4" narrowed upper frame sections.
69 and up all got narrowed upper frame sections to make production much easier.
My buddy had to make some scallops on the frame of his son's 67 C-10. It has a 6.0 LS in it with Camaro headers. Looks custom and cool!!!

[Radford46]

Looks like I’ll be getting out the grinder. Shouldn’t be a big deal. I wonder if the late 68 had the narrowed frames and early didn’t. Mine definitely does not.
Next question is how much of the top frame has to do be narrowed to accommodate other parts of the big block?

[Radford46]

Thanks for all the frame pics Richard, that helps a lot.

[richard2717]

here are measurements. I would assume the cut goes that far back for manifold clearance.

.

[Radford46]

You read my mind, I was going to ask you if you would do that. Thanks again.

[Radford46]

My pretty newly painted frame is going to take a turn for the worse!

[richard2717]

Glad to help. Good Luck

[Radford46]

I finally got a break in the rain and went out and trimmed the frame rails. With your measurements it went smooth. Thanks again.

[richard2717]

Looks like it turned out pretty nice.