I have got my grandfathers 87 extended cab pickup that I plan to restore and was wondering where I could get replacement parts, mainly interior such as rear fold down seats, console, dash etc. Thanks

 

Junk yard or someone parting out or maybe the dealership.
No one makes repop or aftermarket parts for these trucks like LMC or Brothers does for the big 3 makers.

 

There isn't an aftermarket restoration catalog for these trucks , so as Robert_m said you will have to look in different places. Many mechanical parts can still be bought new from Toyota, however, Toyota has discontinued most interior and trim parts. Most interior parts can be found in salvage yards, Craigslist, eBay, the forum classifieds, etc.

Yota Jim's is a Toyota Truck salvage yard in Denver, CO and good place for hard to find and discontinued Toyota Truck parts.
http://yodajims.com/