Ultimately, I guess it depends on what you want from the bike... BITD, and still now, people regularly modify their bicycles with upgraded forks, often pushing the A-C measurement beyond what the original rigid forks had. IMHO, it doesn't affect a bicycle's handling nearly as much as some would have us believe.
As a more extreme example than what you're contemplating, over the last couple years as my wife's MTB skills progressed, I've upgraded her once rigid Hardrock AX ('97) from the OEM rigid chromo fork to a crap Judy J1 80mm, to a Magura Asgard 100. The Asgard's AC length is a whopping 476mm. That slackened the head angle a couple degrees. She came back from her first hard riding experience with the upgraded bike (on trails she's very familiar with) commenting only on the better suspension and surer handling (no doubt due to the stiffer Magura fork over the crap J1). Her head angle has been slackened by some 3 degrees, from something near 69 to more like 66 (neglecting sag, which adds a degree back in). Actually, it's put the bike's geometry largely in line with more relaxed modern offerings...
Adding 30mm to a fork on a bike with a wheelbase of about 44" changes the head angle less than 1.5 degrees. At worst, it'll remove some of the mid'90's nervousness from the bike's handling on fast downhills, IMHO.
J