u can get the spring for the door handle off of a 620 pick up they use the same one. if it is broken it won't let the inside door go all the way shut so you can not lock the door from the outside
on the quarter window glass seal i used a peterbilt door seal, one door seal will do both of the 1/4 windows with about a foot to spare p/n R60-6001-650
Here is what i did with mine, and good luck with whichever build you go with. it old have not updated in a long time.
http://datsun1200.com/modules/newbb/viewtopic.php?topic_id=49008&viewmode=flat&order=ASC&type=&mode=0&start=0