After a good hard look at whatever you can to determine if it's rotting from the inside out (I kinda doubt it, but you never now) you might want to investigate a chassis stiffener as a means of support as it ties in up front right where you need it too.
A sump guard can also go a little ways toward taking a bit of flex out of the front frame legs around the engine. (it sorta boxes in the center rail and forward rail taking some of the torsion flex away)
The stiffener together with a guard can really bring it.
Still, I've not heard of one flexing quite like you describe, or at least not super noticably, so you'll likely want to invesitgate very closely before dertermining your plan of action.
A sump guard can also go a little ways toward taking a bit of flex out of the front frame legs around the engine. (it sorta boxes in the center rail and forward rail taking some of the torsion flex away)
The stiffener together with a guard can really bring it.
Still, I've not heard of one flexing quite like you describe, or at least not super noticably, so you'll likely want to invesitgate very closely before dertermining your plan of action.
