Another consideration on non-OEM hoses: you are dealing with three different ID's on the fuel tank vent hoses (at least on my car). A check of your vapor tank will confirm your situation. If you do replace the lines,OEM or other, there are two rubber grommets where two lines enter the passenger compartment near the tail lights. These help seal out exhaust fumes, ...etc. They are available at Banzai Motorworks. I don't think you should consider doing without the vent lines in place.
The purpose of the tank is to collect the fuel vapors coming from the fuel tank and avoid pressure buildup. Check the plumbing, you likely have three vapor lines coming into the collector from different points on the fuel tank. There should be a fourth line, much smaller, at the top of the collector tank that connects to a hard line going back to the engine to burn the vapors. The three main vapor lines will cost about $210-225 to replace (parts cost only at Courtesy Nissan). I just picked up mine this week as part of my resto project. Hope this helps.
To the best of my knowledge, the original hydraulic shock inserts supplied at the factory cannot be rebuilt, only replaced... if you can find them (and yes, some are still around). My recommendation seconds others above: go with the newer gas-filled insert cartridges. If you decide to go with lowered springs, be sure the new gas shocks are compatible, such as Tokico HP. Not all brands work with lowered springs.
If it is the flat panel that has the hatch striker you are looking for, try Banzai Motorworks - item BO-56, for a replacement panel. http://www.zzxdatsun.com/catBits.php
So glad to see you bringing this classic back to its original 920 gold. Awesome effort! FYI - HLS30-01228 lives just up the road from me in Plano TX, is also 920 gold and is going thru its own restoration to original (my car is also 920 gold).
Video of cars in the Beale Street Judged Car Show. Early 1900's blues music by Bessie Jackson "Barbeque Bessie" and Memphis Minnie "Down By The Riverside"