I have a few 1/64 trucks that I'd like to "lift" in order to fit some bigger tires under them,is there a good way to do this?

you can either grind the axle channel deeper,with a hack saw,

....or you can epoxy (2) 1/32" id, square plastic tubes to "file-flattened axle areas" on the other-side(bottom) of the chassis.(hobby stores carry them)
Hopefully,your wheel pulls off the axles, so you can thread them through the tubes.

Either that or buy a couple JL Zingers and use the protruding rear axle for both front and back, That'll lift the thing. :)

How about using "Donk" chassis's??