I've been there done that. With Z motors and ford 302.
Save the 240 and 260 motors. maybe they'll be worth something some day. The 302 is 50 lbs lighter than the chevy or
the datsun. Also, since the distributor is in the front, the ford 302 is like it's made for the 240,260,280 datsuns. I'f you use a motor plate, you can git it to serve as the strut tower brace, and front motor mount. As far as trans goes use the T-5. There cheap and available.
As far as the swap. This site has at least five, very detailed and proffessional swaps with pictures, and what you need as far as parts
are concerned. Not to mention the aftermarket. READ! No other site has the combined knowledge of these guys. Not by a long shot. Good luck.