people say you can still get them into manual tunnels but with a fair bit of massaging (I personally wouldn't do it as I feel the box would bee too close to teh tunnel and if the motor shifts at all the box could touch on teh body making a banging noise or make the car vibrate?

I've just cut out most of my tunnel and am just going to get some sheet metal and mould it to the desired shape and weld in.

One question is what gearbox are you intending on using if you use the stumpy skyline then just a whole lot of massaging, however if you use the silvia 5 sp then you will have to cut out the rear section of the tunnel and make up a box section and get that welded in, as the rear of the box is shaped up at the back.

Cheers
Damo