Funny to know pwople like this exist!

Old tire is the classic engine rest in a pinch. I’m not intimately familiar with every cab over ever made- VW’s like the old buses could be jacked up over the engine and engine slid out from under easily. Many other vehicles can have the engine out the bottom too- but you need a jack tall enough and strong enough to lift that truck to about waist height or more my best guess- to get the engine out the bottom unless it’s designed to let the engine come out that way (but it doesn’t look like they took the front of the truck apart to clear an engine.)

Most cab overs the engine comes out the top. Hang a couple sturdy beams across the rails and use chains to slide the transmission off. But how did the engine come out? Well- there are at least two people there. We know that. We don’t know much else. With a winch truck you could lift the engine out and set it on the tire. Why? Well- if you’ve got a big truck far in the field that needs engine work- sending a rig big enough to bring it back there and back with the truck would add cost and extra down time. By to mention that truck might be on its way somewhere and so now it needs to make that trip again once it’s fixed.

Plus you need a truck big enough to tow it. So if you can repair in the field that’s probably best- and you don’t need a truck that can tow the cab over+trailer- just one that can lift the engine. Cheaper, easy, more efficient especially in remote areas.

If they don’t have a winch truck or hoist- you could still likely rig something up that would winch the motor out with chains, pipe, etc. and physical labor from a few strong dudes.

With no hoist or anything- bare hands- I’ve pulled and dropped engines up to about 300 lbs by myself (in my younger days...) a tractor powertrain can be about 3,000lbs this is a wee bit smaller- and we don’t need the transmission etc. we could cut the weight down below 900 lbs by removing accessories, manifolds, etc while in the truck, and you probably don’t need or want to pull the cooling system with the engine- so that all helps. So 2-3 strong folks, especially with mechanical advantage, could get the engine up and over without externally powered means.