18x9 +30's should be fine for the front. Your brake set up should be about the same as mine for track width, mine are +35's but it's a small difference. The other thing is to look at 18x9.5's, it seems like there's a lot in the +30 to +40 range for aftermarket wheels in 18x9.5". And that should be fine too, I'd lean more to +35 with those. If I buy another set of wheels for the front they'll probably be 18x10's.
Really the 275's aren't that big of a deal as long as you've got 6" of backspace. Maybe a trim on the corner and a little lip rolling, the rest is ride height dependent and most folks don't run as low as I do.
Yeah the suspension isn't the issue for me in going any lower, the wheels hit the body and that would be true of any kind of suspension up front. Maybe even more so with the HDK, the way I'm set up with my QA1 LCA's and bumpstop I should be on the bumpstop at about the same time my tires touch the inner fender. Apparently there is a
little bit of overlap there...
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This will be my next major bodywork modification, I'll add the tub to raise the inner fender (72BBswingers old ride)
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Yeah an 8" wheel with 4.5" backspace isn't enough. For a 245 the minimum would be about 5.25" of backspace, and that would put the outer face of the wheel in the same place as my 275's. Ideally you'd want more like 5.5"-5.7" if you wanted to avoid doing any trimming/fitting. With a 17" rim ~5.7" is the maximum backspace too, just FYI. A 17" rim doesn't clear the outer tie rod end much beyond that. With an 18" rim the outer tie rod end fits inside the lip of the rim, so you can run more backspace (6"+) which is what you need to step up to 275's.
My Doug's headers sit around 3.75" to the flange on the low side. It's not bad as long as I take it easy on speed bumps.
