Yeah, holy Christ. That would be a difficult hole with a moderately
sized drill press. Or a milling machine for that matter.

I would think you would have to predrill the hole for web clearance,
perhaps 3/8", then drill the 1 1/2" hole.

You could probably do a few without a magnetic base drill, but 300?
You're nuts. Your wrists will be ruined

485 RPM sounds fast for that diameter. I expect it would chatter and
get hot, reducing useful drill life between sharpening to perhaps a few
dozen.

If it were me, I'd want to use a 40 amp plasma cutter and a fixture.
Then I'd ream it out to size with a tapered reamer. I'd guess 300 would
take about a day.