Download the -34 TM for instructions for timing the Engine/IP. If the engine has sat for 20 years, its seen no Bio crap fuel. I would time the engine/IP pull the IP and let it sit in kerosene a few days. Let it drip dry and put it back in. I would bet more than my lunch money that it would fire up and run just fine.
On top of the IP, where the little red cap is. The "T" fitting. Underneath the "T" fitting is what looks like a normal brass fitting. Its not. Its a check valve. Make sure you clean it out.
I am sure I don't need to tell you how to replace the IP. But do rub some grease on the two seals on the IP shaft. The right hand seal tends to roll over when reinserting. And if the oil pan fills up with fuel ultra fast, the seal rolled over.
I would keep the engine over temp switch. Have it turn on an idiot light on the crawler dash.
Some of these engines, back in the day, had been rebuilt a good number of times. The crank, was worn at the front and rear main seals. Its just a tad worn, but after a few weeks of running, started to drip. Front and rear. So keep an eye out for it. We had a whole fleet of em leaking. Tear it down and replace the front and rear main, and....................... a few weeks later, the same thing. White engines had a replacement set of seals. The army answer was to simply put new cranks in em. I love this engine. Its a work horse. I never saw an engine self destruct. And we ran em 24/7, 365 days a year.