Crossmember/frame differences (a rant)

[shifty]

Ok, so, I jsut want to have a little "Mythbusters" session about frames and crossmembers.

There are two major differences that make a '73-87 front crossmember (possible 71-72 as well) NOT a "direct bolt on" to a '68-'68 frame.

Back story: I picked up an entire '73-'87 front clip and rear end recently to swap into my '68 from another board member/friend. I got a killer price from him, and it's in great shape, so I can't complain now that i'm finding I can't easily use it. I want all of you to learn from my experience.

I cannot even BEGIN to tell you how many different times I read all over this forum that this would be a direct bolt-on swap, that the '73-87 front crossmember would fit like a champ in my frame with nothing more than "warbling" out one or two holes a bit. THIS IS ABSOLUTELY NOT TRUE.

I'm here to set the record straight after spending 5 hours today taking off brake lines, unbolting parts, cleaning up suspension and brakes, pulling off wheels, and finally swapping to my mid-70's crossmember.

Here's the problem:

1) The framerail on '73-87 trucks is 6" tall at mid-crossmember. The framerail on 67068 trucks is 5.5" tall at mid-crossmember.

This matters to me because I'm using the ECE GenIII engine mounts for my LS1 swap, and they incorporate the '73-87 stands, so while they are a perfect bolt-in for the '73-87 frame+crossmember, they require drilling with the 67/68 frame using a 73-87 crossmember.

2) There are four bolts that hold the crossmember to the frame on the side. They use a completely different pattern in 67/68, so when you go to bolt that 73-87 crossmember to your frame, two of the four holes line up perfectly, one hole needs to be "warbled" out to make it work, and you will need to completely drill a new hole for the fourth bolt. Be aware. The other pair of three holes on the bottom of the framerail seem to work like a champ. On a positive note, the access holes for the press-in studs for the upper control arm are perfectly accessible .

Anyway, that is all for my complaining for now. I just wanted to share my experience with others so you can learn from my mistakes.

I know some guys would be like, "Dude...just modify it!" But you know what? I already modified my old one and it was working. I swapped to 73-87 so my ECE GenIII mounts would fit like a champ...I dunno about you, but I don't want to do work I've already done, and swiss-cheese my frame in the process