I haven't tried not using a servo saver at all. Seems like steering would receive a lot of stress. I use the HD servo saver spring.
Trenchers are fairly heavy so you would need to gear down. Axial 8 spoke oversize seem to have a good rep for a 40 series wheel.
Shock tower supports were part of a custom XL build I did last year
http://www.rc-monster.com/forum/showthread.php?t=26870