Endless stall issues

Hey everyone, I'm hoping someone can help with this issue that is leading me to pulling my hair out. Let me give you a bit of a backstory.

I bought a 1992 Toyota Townace (automatic and carburetor), in Melbourne and converted into a camper to travel round Australia (from UK originally). Paid a reasonable amount from a wholesaler who was very good (although has since not returned our calls, surprise surprise), sorted out the roadworthy and left Rego on the car, also let us test drive the van without him for considerable time. It ran really well, occasionally roaring at idle (in park/neutral) but would fairly quickly settle back to normal (when in drive/reverse).

I drove a fair few thousand Km on it, Melbourne along the Great Ocean Road and back, and then headed toward Sydney probably notching up about 1500k in the process when suddenly the temperature raced into the red leaving us broken down on the side of the road. Luckily, the day before I had signed up to RACV, and arranged a breakdown truck to pick us up. Our mechanic was ace, super helpful and after diagnosing our issue as a cracked head (the last thing I wanted to hear) offered two solutions; Fix the head, paying a huge amount in the process, or using a seal (some kind of liquid glass). Obviously, after living in a tiny room in London for the last 8 months to finance our trip, I elected for the seal, fully aware it was a temporary fix. The mechanic also fixed put in a new thermostat, meaning the temperature gauge read around 1/3 (having before sat at 0) and as a precaution I often drove with the heaters on.

Guess what? We made it to Sydney without incident. It was here we met my partners cousin, who, after hearing our head troubles, offered to change the entire top end. New head, gaskets and radiator. It took approximately 18 hours, several cases of beers and helped me, a noob before, learn a ton about my van. However, after putting everything back together we encountered a stall issue, at first all the time. However, the more we worked on it, tweaked a few things it became that it would idle like a champ, then stall once put it into drive/reverse. And after that it would idle okay in drive/reverse initially but when braking/slowing (ie no revs) it would then stall. This makes it very difficult to drive, and potentially unsafe as the brake assist fails once the engine stalls (being the financially focused travelers, I only have the most basic insurance).

In the process of trying to fix this issue we have gone through a number of fixes.

- checked for compression/found bent push rods and replaced
- checked for spark/replaced spark plugs
- replaced nearly all vacuum hoses (95% sure they have all gone back on correctly)
- cleaned and rebuilt carb (brand new gaskets, set the float height etc)

The carb clean/rebuild was on recommendation of a mechanic who we took the van to, who couldn't find anything glaringly obvious otherwise.

Still no luck. We have since tried running without the EGR (due to snapping bolts in manifold we welded it shut), nothing. Have also tried switching vacuum hoses round but as I say, 95% sure that they are as correct according to diagram, but due it being automatic, it's an absolute maze under there! It's also running very hot, although maybe this is as the new sensor is calibrated differently.

All in all, I am becoming very frustrated with this and it's cutting in to my travelling Australia time. I'm getting tempted to book in with an official Toyota mechanic but we've already spent a substantial amount trying to fix this problem and would like to go skydiving so any help would be much apprecited!

Please let me know if you have any tips... or I might kill Ash (the mate/cousin who helped/broke the van).......