Hi Stan,
The inside width of the car shell that I propose to use is 39mm, the interior length is182mm between the mounting posts and the interior height is 38mm. The chassis of the donor car is of sheet metal construction. The chassis is from a Gilbert AF operating box car and the shell that I will use is from a Lionel Flyer Christmas car. The shell and chassis will fit with minimal mods to the chassis. I am considering using a dc-dc buck converter and putting a 1000uf 35v cap between the rectifier and the buck converter to even out the power in the case there may be dirty track, might that be a good idea or am I all wet?