OK this is the gear box I used, I went with the 115:1 option since it seemed to be the one that has worked best for people in the past.
Again from folks that have done this in the past I swapped out the 3v Tamiya motors for these slot car motors
I got them here
https://www.professormotor.com/product-p/jkm7.htm
They are a a 48k motor at 12v so they will be fine at 7.2v.
I made a simple cardboard template to drill some mounting hols in the loader. The transmission fits snug in the body I used some plastic tubing to make some small 1/8 in spacers where the bolts go thru and it pulls the sides in straight and keeps everything solid.
The axles are a hex shape and to small for the bruder plastic wheels so first I knocked off the edges on it then put them in my drill and spun them against a file to round them out and cut them to about 3mm. Now I have to figure out how I'm going to mount them to the wheels. I have some brass tube just need to work out the details.....
