John,
Since the front coupler of an F-unit is generally more show than use - except in the case of MU'd A-As, I would go with either the semi-scale #58 or #158 coupler. That said, I use the #58 on all my locomotives and rolling stock and they work very well.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Doing the Kadee (#450) close-coupling mod seems to be a common upgrade for Stewart F units. Would that normally include both ends of B units? I'm inclined to think so as multiple Bs would be MU'd in the course of regular operations and the prototypes would be delivered with the same specs on both ends.
I'm presuming in all this that simply doing short-shank replacements is insufficient to close the gap to the next unit to three feet.
And while we're at it, what Kadee (whiskered or not) would be appropriate for the front of the As?
May have to buy a few extra packages.
Thanks, guys -
John