Excellent choice of wheels :agree:
On my '74 Standard, I'm running the same wheel size as you with a 235/35/18 and 265/35/18 size tire. The wheel/tire combo is heavy, 47 lbs front and 52lbs rear, but I notice no ill effects in driving. The car handles incredibly well and the contact patch of the front tire makes stopping a breeze. The turning circle is not so great, but I'm set up for street cruising/circuit racing and not autocross so I don't mind.
I could get up to 190 KPH with my old 195/65/15 rear tires (pre GL, T4 motor, stock T1 trans), and with my new setup, could still hit 190 KPH with the 18" wheel/rubber. I'm running a 901 now and 190 KPH is still not a problem. Acceleration is still awesome with the 18 inchers.
I am using 2" widened fenders all around so you don't have to go crazy on the fender widths, and if you use a front bumper on the rear (front bumper is wider than the rear), it will look close to stock from the rear, except for the huge boots under the rear fenders
I'm using a 3" dropped front beam raised all the way and CB dropped spindles. The front wheels (24.5" dia) are close to stock diameter so speedo is fairly accurate, and the wheels tuck nicely under the front fenders.
I wanted the section height of the front and rear tires to be close to the same as nothing looks sillier to me than a small section height front tire and a rear section height that is 2 times the size .... it looks like the wheels belong on 2 different cars.
I hope this information helps you out a bit in choosing your setup.
Sandeep