Long to short bed help

[stangboy88]

So I have came across an extremely nice 68 lwb chevy that was resto'd in 90's and then has started to age since. The floor will need a little work for a patch but the interior is very nice. With a solid 350 it'll do for now until I can find a 6.0 to drop in. Anyways, what is the view on the forum for cutting the frame to shorten to a swb chevy? How much do I have to cut out? I saw it on Trucks TV when Stacy was still on there and he cut 12" off in front the rear wheel, correct? How much would this cost a shop to do? Worth me doing it in the shop?