Be careful using the 274A as a direct, drop in substitute for a 5U4G. It will work just fine IF the design of your power supply will support it. Assuming you have a standard CLC filtered power supply circuit, the first cap after the 274 can be no larger than
4uF according to the published data by Western Electric.
If you install it with a first filter cap larger than the 4uF, it will
work.....for a while, then it will self destruct likely taking out the power supply transformer and at minimum the first filter cap and likely the choke follower when (not if) it shorts out.
That said, I have no idea how the Shuguang specs read. They may have deviated from the WE design...which wouldn't surprise me.
The 274A in a proper circuit can sound wonderful. Cleaner, more open, blacker background, it is a great rectifier tube. You just need to be cognizant of the design of your power supply.
For those curious, you can download the spec sheet on the WE 274A form this site.....http://www.mif.pg.gda.pl/homepages/frank/sheets/136/2/274A.pdf