I would like some help id'ing this bike. The front badge just says ross allentown, pa. the rear derailleur is a shimano lark II. front derailleur says thunderbird gpo. yoshikawa brake levers. the shifter says shimano on it but i have no idea what model and it's a 10 speed with 26x 1 3/8th tires which are new.

from reading some posts it seems like it was a low end bike. any idea what the model is and what kind of upgrades can be done on it?