I ran 10.9s on the XE284H junker, with a best of 10.91, all this shifting at 5600, there was a 10.8 in it i'm sure, so yeah i'd say there crappy & don't make much power
, But i will say most of the lifter clatter is do to running run of the mill hyd. lifters, the magnum lifters they sell with the kit are junk IMO, clatter city after a few thrashings, So i learned my leason & went with the "pro-magnum" (anti pump-up) lifters & never looked back, there a much better design & are for high RPM, they carry a heavier C style clip & can be run at 0 preload. I'd rather hear a valvetrain have a mild solid cam like sound but know i have the added peice of mind the lifters are going to handle it & no fall apart!
With such a mild 440, i'd run the XE274H & call it a day. But you can go with a custom grind like mentioned from Bullet, Isky-Racer brown exc.