[OBeer-WAN-Kenobi]

I didn't have to modify the tunnel in my 69 either but it was close enough that I had to cut out the little body nuts that are used to attach the stock console. That gave me about a "finger"of clearance in that area but more everywhere else. You may have to make some clearance for the reverse lockout as well.

I also had to tip the engine down quite a bit too get the transmission installed since I already had the subframe in when I did it. The bellhousing was hitting the tunnel and not allowing me to line up the input shaft. Once I got the transmission attached though, I was able to tilt everything back up inside the tunnel.

This is all pretty much completely dependant on what frame stands, engine mounts and adapters you are using. Same with headers and oil pans. The lower the engine sits and the more forward it sits, the less likely you'll need to modify the tunnel but the more likely your headers will hang low and more likely you'll have oil pan clearance issues with the subframe and steering.

So, you have to find a happy medium.

Mine has an LS engine, but my mounts "supposedly" set it in the stock small block location. I'm any case, I'd you're using a SBC, my info may or may not be useful.