Recently put one in a 71 Dart Swinger with a 904.
Splitting the tunnel and making a raised area under the seat was mandatory.
In this cars case we had to remove the exhaust and redo it because he had an H that was right in the way.(basically moved the H forward more by cutting two straight sections ahead of the H and putting them back in behind it)
No mods to the cross member, but the driveline had to be shortened (no vibrations)
We split the tunnel about 12 inches down one side and across the top to the other side, lifted that and then welded metal back in the gaps to create a 1.5 inch rise in the hump giving about 1 inch clearance all the way around.
The wiring was easy, and we added a relay to power the solenoid.
I see people talking about gear splitting, but in my own opinion doing it manually without the electronic controller just isn't worth the effort.
The guy that owns the car brought this up and I asked if he thought he was fast enough to manually change gears along with the in and out of the OD to make it worth it, and he agreed there was no way.
I teased him about by the time he finally got into 3 OD I would be so gone he wouldn't even see my tail lights at night.:D
After all the above we found that the pump in the OD was shattered and it wouldn't work anyway.:BangHead::D
