A year ago I bought a K-4880B Pennsylvania Brunswick Ltd 15" Heavyweight 4-PAC. The set is illustrated here -- http://www.legacykline.com/app...mp;p_oem_sku=K-4880B
I like it and enjoy it, but it does use a good bit of amps and there is no interior seating/passengers ... the 4-car set uses silhouettes on all of the side windows.
Now considering upgrading to LED lighting and adding passenger seating and passengers. Don't want to spend a lot of $$ nor spend a lot of time on modifying four cars. Would like OGR forum member experiences/recommendations. I am aware of GRJs LED lighting mod available via Hennings Trains. I have also found a couple of web sites advertising ready-to-go passenger seating inserts, but don't know if they'd fit my cars. I am attaching couple of photos of the interior of one of my passenger cars to help with your considerations for modifying my cars.
Note that there is a 2-wire connector on the floor of the car that electrically connects the front and rear trucks. That is likely in the way of a ready-to-go passenger seating insert.
Edit: Just noted a thorough 2019 OGR post that documents modifying K-Line passenger cars ... https://ogrforum.ogaugerr.com/...upgrade-k-line-k4690 Very good work. However, if possible, I'm looking for a ready-to-go insert that just fits into my available floor space. Don't know if I have the patience to do the detailed work demonstrated in the above OGR forum link ... for 4 plain-Jane passenger cars.