Will a 1911 Colt 9mm Luger clip work in a Colt MK IV Series 70 38 super auto?

probably not...................

The magazines are similar, but the 9mm has a spacer in it on the rear of the magazine to accomodate the shorter 9mm cartridge.

New magazines in both calibers are available from Colt on their web site (Coltsmfg.com).

Ps: a "clip" is a strip of metal made to hold rounds by their base, (google firearm clip) a magazine is a spring loaded box like receptacle where you put rounds in.