Sounds good... so it seems there is alot more parts involved in a 360 swap than just a 360, lol! Ugh, it's been nuts just trying to find everything needed.
I've learned that the 304 and 360 flexplates are so close (down to the tiniest fraction) in balancing that they will work for each other. I've also learned that you can take the flywheel off an automatic with the correct 360 balancing and have you 258 Flexplate balanced to those specks. You just take them both into the machine shop and tell them that you want the flexplate balanced the same as the flywheel and all will be done. This is also much cheaper than buying a new flexplate.
And as mentioned before, you need a smaller oil pan. Not just any Jeep 360 is going to work, you need to get an oil pan off of a passenger car. Luckily, in my search for information... I've found a NICE AMC bone yard that doesn't crush, only 25 miles from me. Not many Eagles left, but plenty AMC 304's and 360's from Ramblers and Javelins. Lots of those cars intact laying around there. I didn't have time to snag photos but I will be heading out there again soon to check everything out and maybe post some parts for anyone interested.
So yeah, even with a good running 360 and a solid Eagle... it's no simple task installing a 360. You're much better off digging one out from a passenger car in the first place.