Installing two 12" subs and amp in a double cab?

The shok triton 12 is about 6ish inches in mounting depth.
I don't know how old your type R is but measure it and check.

Like i said, follow zman2k2's build and you should be able to get them in if your close to 6 inches in mounting depth.
As for your amp, check if you remove your under the seat storage bin if it fits in. IM worried about the amps width

 

Yeah, that too. They are kinda deep. Mounting depth is almost 6.5"

 

6.5 may be hard without fibre glass