A shake at highway speed that comes and goes is often related to tire/wheel balance.
I know you just had the rims and tires replaced, but it's possible one of the old ones
and one of the new ones are both unbalanced. Since you mention the rims are aftermarket,
do they have the correct 56.1 mm centerbore or centering rings? Other possibilities
include warped brake rotor (shouldn't be noticeable if not breaking), or some play in
the front control arm bushings (very common problem with stock bushings, won't happen
for a long, long time with powerflex bushings), tie rod ends, outer ball joints or inner ball joints.
Upper strut mounts often crack and split, but unlikely to give these symptoms alone.

I'd bet on tire/wheel balance or worn FCA bushings first.

 

Make sure lug nuts are torqued. Check lower engine mount for wear.

 

check the front wheels for free play, ive seen a few where the driveshaft nut comes loose and gives you major play there, otherwise as mentioned the castor bushes crack over time and also check the drivers side engine mount it is a hydrobush that leaks its fluid all down and around the chassis rail when its flogged out

 

Thanks for the help.... ill check each of these issues...