Aftermarket rear struts (aka hatch lifts) can be sourced brand new from strut specialists.
Just take your old ones in and they will find a close match.
They are generic parts - no special brackets or anything.
I'm not familiar with the pressure relief valve - here in Australia we didn't get electric fuel pumps until we also got fuel injection (which uses a high pressure pump).
But Toyota often uses the same parts across many cars.
Look in junk yards for anything of a similar vintage - Supra, Corona, Corolla, Cressida, Hilux (aka Truck).
You can get more help at
http://autos.groups.yahoo.com/group/Classic-Celica/
We concentrate mostly on the first generation (1970-1977) but your second gen 1979 has many of the same mechanical parts as our cars.
- Stepho