It is very heavy to do parking manoeuvres on asphalt, despite well filled tyres and large, original steering wheel. Tyres are radials which might explain it, or part of it. No noise from pump, pulley or anything.
Finevat low speed driving.
Perhaps it´ s all normal…?!
What about ball joints and tie rod ends? Steering Column? Idle lever? Dirty filter in the reservoir?
Put it up on jack stands placed under the lower control arms near the lower ball joints and see how it steers with no load on the tires.
A wider tire patch than original on the ground can contribute to harder steering.
I don’t think it’s the tyres. I have 205 width radials and a 16inch steering wheel and it steers just fine.
I placed 2 magazines just behind the tyres, reversed so that the wheels stood on the magazines, instead of the concrete floor, and then tested the turning. Absolutely fine !
So I don´t think anything is wrong. It´ s just that the steering is much lighter on the 420G and S-type with 420 box and original servo.
My experience was with Mk7s. w/o power assist. When I put on 600x16 tires and wheels the steering was much lighter than when I had Buick wheels on it. Not sure about the steering wheel but I expected 17" from memory. It was about an inch larger than the XKs of the time.