That truck has a one piece rear main seal. Lower the pan, pull the tranny back about six inches. Put two six inch bolts in the lower bell housing holes and slide the tranny back on those, no alignment issues when it goes back together. Take the flywheel off, then take the bolts out of the aluminum housing that hold the seal, and slide it off the back of the crank hub. Remove old seal, install new seal, and re assemble. three hours work with a hoist and air tools. I have done a LOT of them.
Rebuild kit for that engine is about 300 bucks. About 100 dollars for boring and cleaning, and about 45 dollars to get the old pistons pressed off and the new pistons pressed on..
This is assuming you can do all your own work. five hundred bucks plus fluids and tune up to rebuild your own engine. I have done a lot of those too..
Old Betty (My truck).... (One of them) is an 89. I drive it every day, it still runs on the stock TBI, with a 350 roller cam motor out of an 89 Firebird. Computer compatable is a matter of common sense. If it has a more or less stock cam and compression is not too high the TBI will "learn" to a certain point.
I have bolted 350's in trucks and vans set up for 305's My last 89.. that I wrecked... dont ask... had a 383 in it with the stock TBI. I had to put an adjustable fuel pressure regulator in it and venom injectors to get the lean codes to go away.. it ran SOOO nice... This one will eventually get a 383 in it as well.. just cant justify it while the engine thats in it still runs so good.
That 91 is easier to fix than most trucks on the road now. There is nothing you cant get for it.
I will own and drive Betty for the rest of my life, barring another wreck... I get about 14 running about town and 16ish running down the highway with 31" tires and 4 wheel drive. She has heavy torsion bars in the front and ten leafs in the back. A hitch and a gooseneck ball in the bed. it has rubber floor mats and roll up windows. it has a CD player, and the AC will give you hypothermia. The bed is lined and I have aluminum rails on the bed so I can drag the chains out without tearing the paint off.. its a truck, it was meant to work, it get abused, and when i break it, it costs me less to fix it than almost any other vehicle I could own. If I dent it, I cry... when it gets a rust hole, I weld in new metal. It is painted with International Harvester Black enamel, so touch ups match and are easy. Painted it myself for less than two hundred bucks..
Try any of the above on a newer truck and see what it costs. The only better truck to own would be an 80 with a retrofitted TBI because they have solid axles, and the TBI lets it start when the wind is pushing the wind chill to below -50...
I have less than three thousand dollars in that truck, including a rebuilt trans that cost me 900 bucks and the 500 bucks for the new tires..
why did I write a book? To tell you if you get rid of it, you will wish you had it back. Use the van, but park the truck, save the money and fix it when you can. I know you are not likely going to be able to do all the work I mentioned on your own. Look up remanufactured engines. You might THINK it is starting to nickle and dime you to death... You put the engine in, fix he tailpipe, and the heater motor starts squalling..so you replace that.. then the circuit board for the windshield wiper goes, so you replace that.. then the trans starts slipping.....
Yep, it does get annoying, but the fact is, ANYTHING you buy used is going to have problems of one sort or another. When the newness of whatever you replace it with wears off, you will miss that old truck!!!
I worked on them for Chevrolet, went to school for the TBI and have a computer to plug in and get codes and read the sensors, so I do have an advantage.. Wish you lived closer.. I have two 350's on the floor and four in the back of the store. We could update it to Tuned port.
Or if you wanted to go faster?
Just watch where your going and dont worry what the Garmin is Saying...