Hi there, I am also new to the forum. I am 6'2" and 300lb. I have a 1950 COE. I bought it sight unseen and shipped it to Australia and I have no difficulty fitting in the cab, however swinging your legs in does take some work.
I actually step up with my right foot onto the top step and swing my left foot and butt into the cab and onto the seat and then bring in my right leg and foot.
Now for you folks over there driving on the wrong side, my technique works OK over here in Australia, but you will have to mirror this for your left hand drive position.
Like I said, I couldn't get there to trial fit myself into a cab, but I have owned a couple of regular cab 1/2 ton chevy pickups and know that I fit in those, so I don't see that you are going to have a problem fitting. The other consideration might be a lower seat or custom cushion to sit on to bring yourself lower in the cab.
I hope this helps you out - regards