I've seen a used rigid fork for sale that has a 450mm A-C measurement. That would give me 2-3" of stand over and a more aggressive position on the bike. I'm not a big fan of front suspension anyway. I've also been looking at the original specs for the bike. Currently the BB is 13.5" from the floor, originally with the rigid fork it would be 12.2". So the front is a bit high.
Lots to think about.
Personally I think a fork of 450mm A/C is too short for that frame - I wouldn't entertain anything less than 470mm unless you want to end up with an overly steep head angle, which will be as big a handicap in technical going as a too-long stem. Combine the two and the forecast calls for pain.......
Inline post, short (60-70mm) stem and wide (700mm+) bars with the forks that you already have and forget about road bike fit conventions. Get it in some tight, steep techy conditions and you'll see that "long and stretched out" isn't necessarily the way to go.
Yes, you need a decent length top tube (which you have) but not with a huge long stem too. Go wider on the bars rather than further ahead, in other words.
You only have to look at old mtb footage from BITD to realise how crap the fashion for long stems, narrow bars and overly big frames was. Endos galore on stuff that we'd ride with one hand behind our backs now. I have to say, in my defence, that I wasn't as much a victim of this as some but, nevertheless, my 1988 Explosif rides a lot better with a short stem and wider higher bars than it ever did when I was racing on it back in the late 80's/early 90's. Top tube's a bit short now, of course, but you can adapt to it.