Should the pitman slide up any further than this ??

Mine are seated much further than that.
Seems to be 2 spline sizes - 1.250" and 1.125" - for A, B, and E cars - but I've seen a pitman listed (maybe Rock Auto) with a 1.06" size.
Measure what you have and post the info, along with what car.

69 Road Runner

Its worth pointing out that the car originally had power steering which I swapped for manual. The power steering shaft is the same size as the manual shaft. I still have the factory origfinal pitman arm that, although a different shape, has the same size hole as the one in the photo.

Interestingly, I bought a new nut and washer from Mega Parts last year which I went to use yesterday and its too small. It is 5/8 and the thread on this pitman arm is 7/8 fine.

Hmmm...I just did the same swap on my '68 Valiant: PS box had 1.250" shaft, MA was 1.125".
My car may have been switch to PS before I got it, but a pitman for a '68 Valiant from Autozone fit perfectly.
At a glance, the PS arm looked like it would work, but it was in fact too large a spline diameter.
IIRC, C-bodies used a larger shaft.

My dilemma right now is finding the correct nut and lockwasher. Its thinner than normal - about 1/2 the thickness of a standard nut .

and when tightened ends up flush with the stud. That will give you a better overall view of the engagement.