:yup:
that's going too keep you busy for a while , labour of love , ideally could do with a full strip, clean and polish/paint as required . like you say its been sat for 15 years in a shed , so a couple more years whilst you returning it to former glory wont go amiss , good that the engine now runs , you could just keep running the engine from time to time, , whilst you pull the front end out for overhaul and re fit then the back end the same , then use it for a few months of this year ,before engine out ,and clean up refurb as required .
good luck , all the best .
take you time with the rusty seized screws and bolts , penetrating oil and time are your friend here