Tascam 488 tape speed mod

[Docdex1]

I’m looking for a way to add a tape speed selector to my tascam 488. I find I don’t need the extra quality that x2 speed provides, and I would much rather have longer recording time. Therefore I would like to modify the unit to allow me to select normal and half speed, maybe with a 3 way selector switch. Is there any way to do this?