John;
Just curious if you have tried an Associated 9110 Hinge Pin (1 3/8 inch length) for a kingpin? We use them on the oval cars with either Wolfe of WindTunnel springs (they are longer, 3/8 inch, and wider, about 9/32 O.D.) The springs are centered on the kingpin with spring holders to keep them in place.
I would recommend the SG1 9110 kingins as they are TiCN coated (very smooth and don't need to be polished).
The spring are available in either progressive or standard rates (and they are color coded.
)
All the parts can be purchased at either:
http://www.lefthander-rc.com/catalog/index.php?cPath=27
or
http://members.willinet.net/bmurdock/MURDOCKRC
This might give you the front suspension travel that you want.