The '97 came with the larger, 3/4" stovepipe. You will want to install a smaller stovepipe for sure. A 5/8" pipe would be good; a 1/2" pipe would be better. A 1/2" APN pipe that will fit your donor engine perfectly is on its way to me as we speak from Gearhead Echo SSEI. I could turn that one around to you for the cost of postage, but you still need some kind of heat shield for the EGR bore. PM me if you are interested in either of the thin-wall sleeves, the shielded stovepipe, a reduced diameter stovepipe, or an adapter ring.

Combined with a Dorman or APN pipe, this method will provide the largest possible insulating gap between the hot pipe and the heat shield. This method can also be used to repair a perforated UIM. How to install an oversize shield in a UIM

This fix provides a .100" insulating gap with an aluminum pipe and is the easiest fix for protecting a good UIM. Shielded stovepipe

If you can find a Dorman or APN pipe, this method shows how to install a heat shield without enlarging the EGR bore. How to install a 3/4" shield using rtv silicone

If you find a stovepipe with a 5/8" base and want to fit it into your 3/4" LIM bore.
How to adapt a 5/8" stovepipe to fit the 3/4" bore in 95-98 LIMs

RE your donor engine: if the LIM gaskets looked really bad, I am wondering if the engine spun a rod bearing from coolant contaminated oil? Unless you are sure, you may want to drop the pan and check out the rod bearings. At the very least, make sure there is no coolant in the oil pan of the donor engine. It would be a pain to install it and find it needs a crank kit.