New Tires for my SPF/427SB

[Double T]

I've had the BFG's, now running Yoko's, not very satisfied.
Present sizes are 255/60/15 and 275/60/15. Yes I like the look of 15" wheels.
Some vibrations and steering wheel shake, smooths out somewhat after driving about 15-20 miles.I've had 2-3 different types of balancing done with not a whole lot of improvement. I've also tried different tire pressures without getting much improvement.
Thinking of perhaps trying some Goodyear's or even going to the 15" Nitto NT555R's, I'm told Nitto makes excellent tires and they certainly look good. I beleive Nitto calls this a Street/Drag Radial, it is DOT approved, it's V rated which I beleive is good up 149mph. Nitto offers these in 275/60/15 or 275/50/15 which I beleive will work on the front, for the rear's they offer 325/50/15 also V rated. The Nitto's are relatively close to the tire O.D.'s I'm presently running and the width difference (OAW) are as follows: Fronts = +.625" (+.3125" per side) for the 275/60/15, and the Rears = +2" (1" per side) for the 325/50/15.
Haven't checked the prices yet, but it doesn't really matter (within reason) as I am really tired of fighting this issue.
Hopefully some of my fellow snake lovers out there can offer some thoughts on my ideas or perhaps suggest some other options?
I would really appreciate the help. I live in Arizona, so it's generally dry and sorta warm. Sincerely, Double T