I just had an adventure trying to get a crossmember installed for my 4L80e.
I tried to stick to the entire Holley/Hooker LS swap parts system.
The Hooker crossmember is very tight on the floorboard and I believe my body mounts - which I replaced in 1992- are not full height. I simply couldn't get enough room to install this crossmember.
So I gave up after 2 days and ordered the GForce crossmember.
It was a piece of cake to install. I highly reccommend it.
Consider yourself warned if you go with the Hooker.
68 Camaro convertible, 6.0 LQ4 with LS3 heads, Vintage Air, 750 street demon carb, eddy perf rpm, GM hot cam, Hooker headers, 4L80e, 12 bolt, 3.55 gears