You might actually investigate switching them around. The 85 supposedly sounds good in the bridge (I know I would prefer it there), and the 81 seems too trebly and too scooped to be in the bridge. There would be no balance whatsoever if you did the 81 bridge 85 neck thing.
They should fit in without modification, I believe.
About EMGs for metal: to each his own, but I would personally take DiMarzios over EMGs for metal any day of the week, absolutely no contest. I have an EVO 7 in my RG 1527 and a Tone Zone in my RG 570. The only thing I'll say about the EVO is that it replaced a Lundgren Model M, and I don't plan on changing it. Now, the Tone Zone, in my opinion, is the meanest, ballsiest pickup I've ever heard. My 570 sounds as big as a Les Paul, but it actually has punch and cut. If you've worried about the TZ being too dark... don't. I was a bit skeptical, too, but it's perfect. If you want to, disconnect the tone pot for a bit of added brightness. There are harmonics popping out everywhere on this thing, and sometimes, there is a slight vowel sound to it. It's my favorite ever for heavy rhythm (it has way more mids than any EMG, driving the amp better and actually lending clearer tone, with more dynamics, and the chopped treble prevents harshness), but it's also an incredible lead pup. VERY rich. It cleans up OK, too.
However, if you're completely sold on EMGs, don't let me stop you. Yes, you'll be able to use EQ devices with them, though the EMGs are not well-known for their pristine cleans. If you put the 81 in the bridge, there's no way in hell I'd use it clean, as it would probably be incredibly harsh and thin sounding, do to the insane amounts of treble the pickup has.