MacLean hammered the ball past Mariners stopper Wayne Brown following a good header back from Lee Peacock just before the hour mark.
Substitute Proudlock, making his first appearance since he scored two goals at Bristol City last autumn, anticipated a poor defensive header to capitalise on 81 minutes.
Town got one back right at the death thanks to a Nick Heggerty firing past David Lucas.
Trialist Frankie Simek, an American formally of Arsenal and Bournemouth, played at right-back while Richard Evans played the full 90 minutes.