If your handy with a welder, get some flat steel plate, weld some round stock the fit the hole in your jack once you remove the saddle. Weld some angle iron to the steel plate, position the angle iron on the corners of the pan. Weld a couple large washers to the side of the plate. Once you have the plate on the trans pan, run a ratchet strap over the pan, place the hooks in the washers you welded to the plate. Now you have a transmission jack holding fixture. Unless things get way off balance, the trans should stay pretty level and secure. Slide the trans back just far enough to remove the converter. Install the new converter, slide the trans back up to the engine block. Slowly tighten the bellhousing bolts, making sure the converter spins. Don’t tighten the bolts all the way without checking the converter!!! If you crank the bellhousing bolts with the converter not seated correctly, you will be removing the trans again, this time completely to replace the pump. With the bolts tightened, the converter should move freely.
Good luck, hope that helps.
