The seller gave me cam specs like 224/224 .581/.581 112+4 — how do I read them?

Reading "224/224 .581/.581 112+4":

• 224/224: intake/exhaust duration at 0.050 in lifter lift, in crankshaft degrees. 0.050 in is the industry standard for comparing cams. "Advertised" duration, measured at 0.004–0.006 in, is always a bigger number.
• .581/.581: intake/exhaust lift at the valve in inches. That's lobe lift × rocker ratio (e.g., on Summit's LS cam card, 0.321 in lobe lift × 1.7:1 rockers = 0.545 in at the valve).
• 112: lobe separation angle (LSA), the crankshaft degrees between the intake and exhaust lobe centerlines. It's ground into the cam.
• +4: the cam is ground 4° advanced. The intake centerline is 4° earlier than the LSA (here 108° intake centerline and 116° exhaust), which is common on street cams to help low-speed torque.

Duration and lift tell you how aggressive the cam is; for an LS, check that the valve springs are rated for that lift.