LS Swap Dually Questions - First Timer

[Android04]

I've been reading through all of the facts and the internet for about a year now to prepare for this moment. This weekend I start the process of my LS Swap by pulling the motor from the donor vehicle. So here is what I got:

Donor: 2004 Yukon 5.3L 4L60E - Runs and drives like it's brand new
Transplant: 1985 2WD Dually 400sbc and TH400 are already out of it

Parts Already Ordered:
Dingo Motor Mounts
AC Delco EP381 Fuel Pump
Dorman PN692-027 Sender
Wix 33737 Single Return Filter
Fuel Line's and Russell Fittings
Fuel Injection Hose Clamps

Parts still needing (please suggest if I need anything else):
Poly Mount Inserts (suggestions?)
Standalone Harness (suggestions?)
EGR Block Off Plate (Needed?)
ECM Flash (Suggestions?)
87 Fuel Tank (Maybe)
Speedo Converter Box (Maybe)
Dakota Digital gauges (stimulus check haha)

Questions:
1) What oil pan should I run, I do plan to lower the truck after the swap is done and running reliably for a while? Holy-302-2?

2)Will I need to change out my cross member? If I recall correctly the dually has plenty of room.

3) Can I run my 85 Fuel Tank (brand new) with the 87 sending unit and pump? Or should I just order a 87 baffled tank?

My Dually is currently off in paint so I decided to use that space to pull everything needed out of the Yukon and start parting it out. I won't get it back for a month or so which gives me plenty of time to get stuff knocked out.

I know TONS of these threads are made, and once I have everything above I plan to start a build thread. I appreciate any and all help! I'm excited to finally start yet another journey. I'm basically building this as my daily and to pull a small trailer for our 4 wheelers and to maybe pull my 65 C10 to out of town shows.