For whatever it's worth, that's exactly how my 84 is routed. Or was. I had a massive heater core leak and ran the line from the intake straight over to the radiator. Once I bypassed the core, it didn't change anything except not puking out all the coolant into the passenger floor board and trying to overheat. I'd call that a win.
If it's fair weather, I'd say buy a plug for the intake and use a cap on the radiator. Both are usually available at the parts houses for cheap enough. Should be fine.