Replace 20 ohm full range speakers (Heath GR-36 FM Table)?

[sydsfloyd67]

I have a great Heathkit GR-36 FM only table radio. The speakers are very light thin 5" full ranges without whizzer cones.

I'd like to replace these with 5-1/4" Fostex drivers I recently picked up. Unfortunately there is a big difference in measured direct current resistance, with the originals showing 20 ohms(!). (Fostex are 8 ohm rated)

The radio is very loud already, so the only thing that comes to mind is to add 12 ohms of wirewound resistor in series with the new drivers. Kind of afraid any fidelity might suffer. Any clues on other options, or if the 8 ohm speakers might be OK directly if using only very low volumes?

(Alternately, would like to get a T-amp's board in there and bypass the resident amp (which would fit easily) but also wondering about listening to the onboard radio Tuner with such a revealing amplifier and speakers.)
Thnx for all opinions, -sf