Will a 11-speed cassette fit my Giant SRC 3 frame (~2007)

Presumably you are planning to upgrade the older frame to a newer complete 11 speed groupset. Makes sense as 105 rim brake groups are relatively inexpensive now.

In 2007 11 speed road groupsets didn’t exit, so we can assume your Giant had a 10, 9 speed or less groupset, and a 10 speed or less compatible hub.

When 11 speed groups were introduced the width of the splined free hub body on the hub was made a little wider to accommodate an extra sprocket. This means 11 speed cassettes will not fit on your hub, so you need new wheels with an 11 speed free hub body.

However, some wider range cassettes can overhang the inboard end of the free hub a little and will fit on a 10 speed hub (a spacer is used on an 11 speed hub), but of course you need a long cage derailleur to work with the wide range cassette.

FYI, frame dropout spacing didn’t need to get wider for 11 speed groups, still 130mm for rim brake setups.