[Radioroslyn]

Well I think it works out like this.
6A8 gm550............... 6SB7 gm 950!!!!
P1 Shield................. P1 Shield.... Good!
P2 Fi................. P2 Fil .... Good
P3 Plate............... P3 Plate..... "
P4 G3/5............... P4 G2/4..... Leave P4 unconnected at 6A8
P5 G1................ P5 G1....... Good
P6 G2............... P6 Cathode..... P6 of the 6A8 goes to P4 of the 6SB7
P7 Fil............... P7 Fil..... Good
P8 Cathode............... P8 G3..... P8 of the 6a8 goes to P6 6SB7 P8 of the 6SB7 is connect to the grid cap of the 6A8
Think of it this way. G1 is the control grid for the LO
Grid 2 acts like the plate for the LO
Grid 4 on the 6A8 and grid3 on the 6SB7 is the input grid
The 6A8 grid 5 acts like a screen grid. That's why G2 and G4 are hooked together on the 6BS7 both need to have HV on them.
The 6SB7 grid 2(osc plt) and grid 4 Mixer screen grid.
Don't know what grid 3 does in the 6A8.
Hope this make sense to you.
Terry