Just a small point as to the choice of valve, the original HL23DD valve used in the HAC kits wasn't a good choice as it had a 2V heater. I do wonder whether HAC chose that valve because at the time, it was plentiful and cheap on the surplus market. In the same way, at the end of the war, there were (still are for that matter) millions of surplus acrorn valves - a trimuph of miniturisation in their day. I count myself among those who bought and made a two-valve acorn portable 'camping radio' back in the late 1950s, but as it had 6.3V heaters it made short work of 4 U2 batteries!
If you are trying to make a HAC style radio which looks a bit 'retro' and hence, prefer a larger valve, the 1Q5GT would be a good choice. It has an octal base, but a 1.4V filament, and will happliy work down to low HT voltages, allegedly as low as 18V. Several builders of the 'Hiker's One' and Two have used that valve to good advantage.
The datasheet at the link below will show the data and pin connections of the 1Q5GT:
http://tubedata.tubes.se/sheets/049/1/1Q5GT.pdf
The 'Hikers' radios' have a considerable following 'down under' and might be of interest:
http://www.oldradios.co.nz/hikers/
I'm presently getting the bits together to build a 'Hikers' Two, like this one:
http://www.oldradios.co.nz/hikers/kb7nrn/index.htm
Hope that's of interest.
If you do want to replicate the HAC, you will of course need a Denco green range coil, which command ridiculous sums these days, so may have to wind your own. You may get some ideas from the coils used in the Hiker's series of radios.
Have fun!
David