Some tips, mostly in order:
1. Try not to do this job when the temp is below 20F. Your fingers will thank you
2. No need to go down below. Everything can be done from the top
3. Stating the obvious - disconnect battery ground!
4. Remove choke cable and air intake hard tube
5. Remove two carb to manifold nuts, push aside (I left throttle rod connected, and I have a flexible fuel line
6. The two securing nuts are pretty easy to access. Top one very easy. Bottom one through the side rail cut-out (see point 1, to minimise risk of dropping the nut to the oily abyss below
7. I found it easier to leave wires connected. I just created some slack by disconnecting at starter switch & battery. If you feel brave, go ahead and disconnect before removal
8. Pull starter forwards until clear then pivot rear of starter upwards about 45 deg & pull it out in rearwards direction
9. Don't try to pull forwards past carb then up & out. It doesn't fit - block to side rail gap too small at the front.
My starter is a Delco-Remy, and the solenoid - fortunately - is a standard part used is a million GM applications over 2 decades. Delco 1114256. Easy to get at auto parts store (eg 2SS2 at O'Reilleys). Removing the solenoid is as easy as removing 2 mounting screws, and the one screw for the motor terminal. Be careful with the compressed spring.
When I opened up my old solenoid, I found an oil/water MESS. I did this after leaving the starter inside overnight. I think what happened was, the end cap somehow filled with water, and froze up the plunger. Probably I could have cleaned everything up & re-assembled, but had already spent the $30 by that time. I'll do it later, to have a spare.
