I'm doing nearly the exact same thing right now.

I went with the longer drum: https://www.amazon.com/MiguCo-Stainless-Peanut-Rotisserie-Roaster/dp/B074FQS2S3

And I have bought a charcoal bbq as an enclosure: https://www.walmart.com/ip/Char-Griller-250-sq-inch-Table-Top-Charcoal-Grill-and-Smoker-Black-E72424/341352603

Home depot has a 5/8" threaded rod that I picked up for $1.18 and I got it thru there with a smidgen of work with the dremmel.

It's looking pretty good so far. I picked up an old drill at goodwill for $6 and am going to heat it with a heat gun I have lying around.