there is a small black wire that runs down to the starter solenoid, if u splice into it and run 12v to it the starter should turn.
if u really didnt want to spend $ on a new starting switch , wiring a small door bell type of switch to the starter will be a cheaper way, i did that to one 85 190e reason the alarm unit was dead it also splice the starting too, when unit dont work u cannot get car started.
So I ran s separate door bell switch, later on I discovered the alarm unit and cprrected the wiring, I can use the key to start car properly.

Only issue with own starting switch u will have no transmission lock out when not in Neutral or park, basically start anytime too can be more dangerous in the hands of weak brains!
or atleast locate a power source only when u turn on power, otherwise the switch has no power.

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starting issue fixed, thanks for all of your help. Now onto the next issue. 2nd gear is slipping & I'm no transmission mechanic. Can I get this fixed for under $2000? If so, I'm good to go for another 100K miles. Also, whoever posted that you can put 134R right in was 100% on point. I did it today & the AC is freezing. Total cost: $60 from advance & took 30 min. Dealership wanted $500-$600 & another place wanted $250 for R12.

so how the starting issue got fixed?

if u jack up car, place under stand crawl under the driver side, look up on the trans u should see a vac line goes into a cap, pull the soft black plastic cover off should see a small blank key, pull out a bit and turn right or closkwise, 1-2 notches see if trans firm up also shifts harder, if not turn more.
This is easy way to do.
or dump a can of Lucas trans treatment it may help too.
if it fails then u need a trans rebuild.

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SD300,

I had to replace the ignition switch & steering column lock. I hate doing any work that requires removing the dash, but the cheapest place I found wanted $500. I got the parts from Rock Auto (Starter Switch $17, Lock housing $50). I still have less that 3K in the car (only 97K original miles/one owner)

Just got a new creeper & jack stands so I'll try that this weekend. I just put the Lucas late model gel trans fluid in while charging my AC. It had a slight trans fluid leak too and that should help/fix that as well. As for the trans it self. Once past 2nd it's smooth as silk. I'm tryong to get it as mechanically sound before new paint, etc.