Re: XR274R vs XR280R in 383
I'm running a crower 00423, which is a 277/283 advertised, 244/253 @ .050, and 564/582 lift ground on a 110 LSA. Solid roller.
In a 302, it makes enough vacuum for brakes above 600 rpm. I have idle set to 750 and have yet to have a problem with it. The car does buck below about 1500-2k, but with 4:11's and the muncie that isn't a problem above 7-10 miles an hour.
Personally, unless you are actually going to build something as a daily driver, the benefits of a solid outweigh the ease of a hydraulic all day long.
'69 Z28: X33 / 02B / non-matching 302 / Dart 200cc pro 1 platinum heads / Crower solid roller / matching M21 / matching BU axle / 4:11 ring and pinion