If you skip the rectifier, you won’t use the 5v taps as they are only for the rectifier tube filament. The 6.3v taps are for the other tube filaments (heaters) and the high voltage taps are B+. Be sure to connect the heater with a twisted pair of wires ( for hum reduction). If your PT does not include a center tap for the 6.3v taps, you will need to make an “artificial center tap” by adding a 100 ohm resistor to each of the 6.3v leads going to chassis ground. This is for hum reduction and is especially important in this single ended design. So……the 6.3v circuit will have a center tap and the B+ circuit will have a center tap, if the transformer has any other taps, do not ground them. Either coil up the extra taps and add heat shrink tubing (or tape) to the ends to prevent them from touching anything or cut them off.