Cab over dump truck, autocar xpert tandem, would it work?

Those are tiny. Relatively.

You wont haul too much, probably enough to get into houses for landscaping with a few yards of dirt.

If it has to be cabover so be it, just remember on concrete roads empty you are going to bounce every plate.

 

Used them in construction as mix pavers not at dumps wouldn’t shy away from them if that’s what you need they are nice for a tight spot visibility and maneuvering are nice

 

Only ones I’ve dealt with were single axle units with a truck-mounted Schwarze M6 sweeper body on them. Both were powered by an ISB, and you really didn’t see a lot of space for anything bigger, so, quite underpowered for a tandem. They weren’t horrible, nor were they great… the next two they got, they opted for Freightliner M2 chassis instead.
We have a tandem axle Autocar Xcelsior running a Stripe Hog at the airport. Solid enough build, but they should’ve gone with an engine driven unit, as, running it off the main engine at the low speeds they operate it at, it’s prone to overheating. The Mack DM doesn’t seem to have that issue.
IIRC, Autocar uses a CAN BUS system not compatible with software from any of the major manufacturers, so getting anything on that network serviced poses potential problems.
Now the Xpert does have a flat floor, so if that’s enough of a benefit for you to overlook the rest, there is that. Personally, if I were hell bent on a cabover built as a vocational truck from the ground up, I’d probably lean more towards the Mack DM (which I believe you can still get with a manual transmission) or the Peterbilt 320/520.
Typically, the shorter wheelbase will screw you with allotted weight. If you’re running your own product, it might not be a big deal… if you’re hauling by the ton, you’ll probably get hosed there.