Set back engine or mid engine

Anybody ever moved your engine a few inches toward the rear? I think it would be cool.

Short answer is YES!
When you find original factory ads for these vans, Ford Chevy and Dodge were all building exactly the same size box, but were in a battle to claim the most cubic feet of interior. Diagrams from Chevrolet actually show the passenger seat space and 2/3 of the front floor area up to the bottom of the glass being claimed in this cubic foot race......This is why the engine is placed between the seats in a small sheetmetal box and why these vans were equipped with a folding passenger seat......
Well, If the cubic feet of the interior matters to you, you should leave it alone.... Same if you are going to find the task of Setting mounts for proper driveshaft alignment, lengthening linkages, cutting and phasing the driveshaft and doghouse construction a problem.....Be advised that you could end up with a VERY short driveshaft, so phasing could be challenging....
What you could hope to gain is 1) much better accessibility to your engine 2) Better space and aero inside the doghouse for air flow 3) the space and ability for multiple radiators and coolers that are not placed right next to your leg 4)The use of other GM accessory drive options without concern for interference with the front seating......
In a v-8 van, you would no longer need to work around the axle from underneath to change spark plugs! (simpler to cut access holes though)
Throttle and auto trans can be operated by cable.....It's completely do-able and has been done before.....Just requires skills and dollars!
I'll be moving the engine on my !08 van back 15-18 inches....

Savage built rat in a box big block in a first gen send him a message if your wanting to go that route he can tell you whats needed.

Works great, at least with a long wheel base 108. You can move the engine back 18" and use the 90's drive shaft, or go a little shorter, but drop the motor as well, so that the bottom of the oil pan matches that of the front axle, and the van suddenly handles like a sports car. I ran a 350 turbo behind a 327 doing this, and all these years later, wish I had never gotten rid of it. With the motor in the back, you can then put in a bench seat and ride 3 abreast. Great fun. Since the motor was also lowered, and radiator along with it, I ran a flat floor, doing away with the tunnel, and never had any cooling issues. The new engine "box" behind the seat, had sides coming straight up from the floor rails, making it very easy to work on, but ran wall to wall so that there were two storage compartments on either side; three flush mounted unholstered cushions topped this platform off, making an adequate seat or bed for anyone riding in the back. I just bought a '68 long wheel base window van, 38 years after the original experiment, and hope to build another, this time with four wheel drive. Working in a transfer case will be the hard part, but if you have ever seen the super short driveshaft on a Jeep Wrangler, double Carden joints and good geometry will hopefully save the day. Good luck!

Im new to the Van game,, I have a 68 Sportvan 108,looking for window seals and door seals,,, along with some rebuild stuff

I you could post photos of your mods it would help explain what we are trying to see in our heads

If I was into lifted 4WD stuff, I'd mid-set the engine behind the front axle in a lowered cradle to minimize u-joint angles and likely have the longer driveshaft going to the front....Monster-truck it, and the engine might be entirely below the floor.....