76 and 43 are 21 ft, 6 1/2 in from cowcatcher to rear coupler. I'm unsure about 504 and 14. If you want, I have a couple of original builders' drawings that could help with some of your troubles. (trevlyngamer89@gmail.com). The rails are 24 inches apart, and the engines are 600mm gauge (enough to fit). 13 and 14's drive wheels are 25.6 inches in diameter. 43's are 24 inches.