So for $35 (I'm budgeting $10 for a pack of ballbearings) you have a solid 20mph (clocked it yesterday) rtr 2wd (take out the center driveshaft and take apart the front cvds to keep the axle for the wheels, but removing the dogbones part - just a single screw😉)

The handling is livelier 2wd and less friction/drag.

CAN'T run 3s, so as long as you resist that temptation, you will be golden

You can get slow boat parts, (Wltoys 104009 drivetrain and suspension,wheels/tires ) but the whole car is so cheap, get a spare

https://www.amazon.com/Fast-Lane-Cyclone-AX10-Charged/dp/B07V6XFW5X/

Back in stock https://www.amazon.com/gp/aw/d/B07V6XFW5X/

By far the cheapest way to get this done. Now with the increased weight ( that van has to weight alot) I think the stock motor will burn up - I would switch to a higher turn 550 - I got a 35t pretty cheap - I'll look for a link

What's the Amazon rc you have - name or link?

What's the wheelbase and track/width of the ice cream truck?

For cheap temporary chassis stretch I use a price of vinyl fence post from homedepot/lowes - it's very flexy, but takes abuse and if I like the result, then I can work on a metal one, or keep the flexy.

I have one of these https://www.amazon.com/gp/aw/d/B07V6XFW5X/

That I chopped in half and stretched wheelbase 6 inches ( now it's roughly 17, I think) to fit a 1/6th newbright escalade body.