Here's where I'm at with my parts research so far.
1.) 4L80E transmission from '97 C3500 ($500)
2.) Transmission crossmember from '97 C3500 ($50)
3.) ACDelco 15767858 transmission mount ($32)
4.) PCM tune from Black Bear Performance ($15, price of shipping)
5.) Nelson Performance 4L60E to 4L80E jumper harness with speed sensor ($90)
6.) GM Performance 12554824 flexplate ($119)
7.) Dacco B82 4.3L/4L80E torque converter ($175) - This is a factory converter for a '97 4.3L/4L80E 2500 Express Van
8.) ACDelco 14088764 flexplate bolts (X6, $13)
9.) ARP 230-7305 torque converter bolts (X6, $23)
10.) ACDelco 15729870 fill tube ($20)
11.) ACDelco 1259475 dipstick seal ($2)
12.) ACDelco 15996922 dipstick (Re-use from 4L60E)
13.) ACDelco 15687274 inspection cover ($27)
14.) TransGo 4L80E-HD2 shift kit ($120)
15.) ACDelco 24210956 filter/gasket kit ($32)
16.) ACDelco 15039490 crossmember nuts (X4, $56)
17.) ACDelco 15687110 crossmember bolts (X4, $16)
18.) ACDelco 11516845 transmission mount bolt (X2, $7)
19.) ACDelco 15659699 transmission mount washer M11x30x3 (Discontinued, re-use from 4L60E mount?)
20.) ACDelco 11516754 transmission mount nut ($4)
21.) ACDelco 12337828 inspection cover screws (X4, $3)
And here's the stuff I'm still not sure about.
1.) Transmission cooler lines... it appears there are a couple different options for the lines from the 2500/3500 trucks, and I can't make sense of the diagrams to save my life. Don't want to order the wrong ones so I'm trying to dig deeper into this.
2.) Transmission yoke and/or conversion U-joint... I know I'll need something different to get the 80E to bolt up to my factory driveshaft, but I can't find any definitive info on what exactly I'll need.
3.) Driveshaft length... None of the threads I can find on this swap involve a standard cab long bed truck, so I'm really not sure if I'll need to have the driveshaft shortened or not.
If anyone has any input on this stuff, especially the parts I'm unsure about (or if you can think of anything I'm forgetting), please chime in! I feel like I'm on the verge of wrapping up the research here but the last few things are pretty significant.
Edited 8/17/17 for parts list update
Edited 8/24/17 for parts list update