What is this thing and should I use it on my 69 gmc

[MYOUNG]

I am slowly reaching the finish line on the complete front end swap on my 69 GMC C2500

I bought a complete crossmember with the brakes and wheels still attached including the torch cut frame rails still bolted on. I tore it all down and rebuilt it and I am now going to bolt it into my 69 GMC frame but I noticed that the 84 frame had an internal clamping plate or brace of some kind that looks like it would also fit into the 69 frame. The 69 Never had this part but perhaps it was added in later years to make the frame stronger or prevent it from getting loose??

Do I need this thing or should I add it to my 69 frame??

Thanks

[MYOUNG]

6 out of the 7 bolts on each side holding the crossmember on go through these things. My old frame just had the bolts clamping right on the frame rails.

[RichardJ]

I 'm going to make the assumption that the '69 cross member is the same as my '67 3/4 crossmember.

If you place that piece inside your '69 frame rail, you will see that 2 of the 4 bolt holes line up. A 3rd hole has to be drilled and the 4th hole has to be elongated in order to get the bolt through.
The angle piece riveted to the crossmember that bolts to the frame on my '67 is forged steel. The angle piece on the square body crossmember is a much lighter, pressed steel piece. That, would seem the reason for the added stiffener piece added to each side.

You'll notice the brake lines on the later setup go across the frame under the radiator which is where they mounted the Brake Combination Valve. You may also find holes in the frame where the new brake lines connect to the new brake flex lines. The hole has to be drilled to a larger size, but is in the correct location.

[MYOUNG]

Great. I will drill the additional holes and put them in.