I also have some funky and oddball ideas/theories on how to make it more feasible and lighter. Unfortunately, in regards to automatic conversions, the info available online is very limited. I also haven't gotten a full grasp on how automatics even work, so what I'm saying may sound coo-coo to gear heads.

It depends on what you want. If it's done strictly following a romanticized idea about how the finished car should work and it has to have a manual transmission, even bolder, the original transmission, you're only choice is to buy an aftermarket motor and make an adapter plate and then tune the power and the way it gets to peak power so it doesn't ruin the original or multispeed transmission which electric motors tend to do since they have monster levels of torque, that's why they're used to start combustion engines.

If that is not the case and you just want a solution that makes most sense from an engineering point of view to get the best driving experience fit to the electric drive train, most go for Tesla motors that have custom aftermarket software to make this work and there are some places that sell these Tesla motors that have been salvaged from crashed cars and "hacked" to work outside a Tesla car.

In any of the above cases, it's going to cost quite a bit of money and it's not going to work on a small budget unless you know what you're doing and just need some basic parts. As that doesn't seem to be your case, you're looking at multiple tens of thousands of dollars to get a ~100 mile range EV that is albeit fun but ultimately inferior to a new EV like a Model 3, Kona EV, Kia eNiro, Nissan Leaf Plus, Chevy Bolt etc.

I'm not trying to scare you away, I'm just saying that you'll need outside help and if that's not free from friends, it's going to cost. Companies like EVWest can both sell you the parts you need or do the conversion for you.