[Hallicrafters] Speaker Matching Transformers for Sx-28AU

[Paul Whitehead]

Need help! I am rebuilding (along with other Hallis) an SX-28AU. 
This receiver has 5000 and 500 ohm speaker outputs. When it is done I will be using a Jensen P-10R speaker for the PM 23 cabinet. 
Assuming that the speaker transformer in the radio is okay-what type of transformer should I put on the speaker to match it to the output from the receiver? 
I was told I could use a 70 volt matching transformer but I can't find any info to back this up.
If anyone has a manufacturer, part number and a distributor where I can buy one it would be appreciated. A wiring diagram for this part would also be appreciated.
Thanks to all who answered my last question about an SM-40signal meter
                                Thank You
                                Paul Whitehead