Header advice, and other boiler replacement questions...

New England SteamWorks said:

The boiler you are considering does have 2 each 3" risers/tapings. And it is a fine boiler. If the installation is gas and in this size range, we use either your choice Weil McLain/GSA/Williamson, or Peerless. The gauges and controls are on opposite sides, so this sometimes makes the determination which we use.

You'd be safe with an EG-55 or GSA-200. But if it were us installing, we'd take a hard look at whether we could make the EG-50/GSA-175 work. Bigger is not better with steam.

You do need a new header. The steam supplies need to be piped into the header after the two risers, not one on each. Close, -but no cigar. And any contractor who didn't see this is not worth your time.

@New England SteamWorks I'm considering the Peerless 63-05L, rated for 533 SqFt, compared to my EDR calc of 501. The Williamson/Weil options are rated at 521 SqFt which is a better match, but it seems Peerless gets more praise around here. Is the difference of 12 SqFt between the two negligible?