Model A starter reinstall

Can someone out there please tell me the easiest way to reinstall the starter on my 51 Model A? It was pulled out and rebuilt by someone else and now I want to put it back in. Huge problem from what I see! There isn't enough room inside the frame to install it without having the cables attached. Yet there isn't enough room to get it fully in position with them hooked up.
Thanks!

The top where the switch is there is to be a copper strap that extends out into behind the flywheel and the is where the cable hooks onto. I wonder if you have all the parts ? It is a tight fit but not real bad to do. Hardest part is making sure the push rod does not hit the cable terminal when pushed but you can't see it when assembled.

Probably goes without saying,
but I would disconnect the battery before attempting to install the starter.

Adding to what the others said, watch your fingers, and if you do happen to kinda smash one, don't drop it, foreheads and faces don't heal any faster than a finger.

Its real fun hooking up the battery cable to the strap. Getting the wrenches between the flywheel and the main case is tight. I wraped my strap with electric tape to be on the safe side so it wont have a chance to short out. The starter itself is heavy and can be a bear to get it in place from the bottom side .

Yup! Been there. Getting the starter thru the hole in the frame with all the pieces
lined up right was my biggest problem, but it finally worked. And yes, it is HEAVY!!
That extender for the cable hookup is critical...as is getting the starter pedal rod in
place right-side-to!! Also, to avoid having to re-do that exercise, be SURE that the
post that the starter connects to when you step on the pedal (it is a lug in the starter
case and has a flat raised rib that makes contact) IS TIGHTLY SEATED IN THE CASE!!! If
it turns 45 degrees..no contact and you are going to be doing the wrestling match
again!! GOOD LUCK!!

And by the way, as a teenager I was taking the starter out of our 50 B (lighter than the
51 A!!) and did NOT disconnect the battery first. High school ring barely touched the
frame and cable bolt at same time, and I was lucky to pull that ring off before it
burned my finger badly! (The moral..do not wear rings around electrical stuff!!!)

I just put a starter on a 620 and found it easier to pull the flywheel....

When I have done it I'm on a creeper to move freely. Take the fly wheel cover off. Disconnect battery of course, I'm at a 90 degree angle to the tractor with my head under the flywheel and starter on my chest. Insert the nose of the starter into the hole in the case under the flywheel to support that end of the starter. Make sure the starter rod loop is in place around the nose. It must be in place first. Keep the attaching bolts near. Make sure the flat copper pc is attached to the starter switch tightly and pointed towards the front of the starter. When starter nose is in the hole try to attach the top most bolt to hold starter in place while supporting the rear of the starter. Make sure the bolt pattern on the starter and tractor match. I then take a pc of flat iron pre-drilled to match the starter cover bolt pattern (use the cover as a pattern) from front to back of the cavity with one bolt attached to the case to the rear of the starter with the flat iron swung out of the way so when the starter is in place I can swing the other end over and attach to support the rear of the starter. Then the starter is in place and I can move it around to make connections.