Yup that's still my truck just photoshoppped somewhere I've got ton's of drawings of them done various ways, when we decided to build that truck there weren’t very many around, now every magazine I get there's another one. My father and law and I discussed and made ton's of measurements/drawings before we decided to start cutting then it popped up in Iowa already started the guy had run out of steam and was looking to get rid of it and it was pretty much done the way we had planned. I worked on it for a while then got distracted on my 53 half ton then on the 53 2 ton at the moment it's stored up at our farm waiting for me to get back to it.
I'm a big guy too and this was my original reasoning for wanting a long cab. I think you could achieve more room with a different seat or pushing out the floorboard a little. I'd recommend checking out the seats from RodDoors (http://www.roddoors.com) they have a cab they take to swaps and shows that's all setup, I've set in it a couple times and their seat hugs the back of the cab much better and really feels good.

I love my truck the way it is but I like the looks of extending through the doors I've seen a few done that way and it looks good, a little won't be notice by 95% of people a lot will fool them into thinking it's got a chop, the first one I saw like that took me about 5 minutes of looking at it to work out what had been done. A good metal man can make anything work out think about it a lot before you let them cut, a grand sounds mighty cheap for this level of modification I'd get it on paper before they tear into it.

Either way man good luck. Stock, chopped, slammed, stretched, with a banger or a big block I'm happy to see another one getting on the road.

Mongo


Mongo's Garage
Vintage GM Truck's & Parts
https://mongosgarage.com