If your domed pistons will not work with 781 castings, they will not work with 049 as they are the same chamber shape. I'm gonna take a stab at it here and say that you're having issues with clearance on the sparkplug side of the chamber? Many of the forged large dome open chamber pistons (especially TRW/Speed pro) are designed to work with 990/188/088 heads and have a slightly different chamber shape than the 049/781 castings... especially the sparkplug area.
