(I'd make it a fixie conversion
)
Congrats!
You can throw 700c wheels in there without much ado; I put some on a 1980ish Schwinn Le Tour (27" wheels) without much problem -- had to adjust the brakes.
Definitely change the cables.
Remove the derailluers and clean. Months in the elements and rust can wreak havoc. Be prepared to replace...
Then go ride the sh1t out of it!