You will need the flywheel for the 700R4...you will need the starter for the 700R4...you will need the torque converter for the 700R4...you will need the output shaft housing from your current TH350...you will need a dual socket brake pedal switch...you will need your current drive shaft shortened...you will need to drill new trans x-member mounting holes...
You will NOT need to install a computer of any sort.
Basically, here it is in a nutshell:
1) bolt the 700R4 flywheel onto your crank shaft.
2) Install the starter which was used with the 700R4 onto your engine. Some people got the idea that you can use your original flywheel and starter and....whatever...NO....it wont work...you are dealing with metric measurements here and your 70's flywheel wont bolt up to the 'metric' torque converter.
3) Install your 4X4 tailshaft housing onto the 700R4...this will give you the ability to continue using the mechanical driven speedometer as well as allow you to bolt your T-case onto the 700R4.
4) Have your driveline shortened EXACTLY 3/4 of an inch. Any more than that and you may crack the tailshaft housing as the rear suspension travels in its telescoping motion....any less than that and the slip yolk will bottom out and trash your output shaft seal.
5) Buy the appropriate conversion kit which allows the transmission to operate correctly...there's dozens of company's out there selling these things....average price of a kit is right around $130...it will come with wires, sockets, a servo, a pressure switch...if you get the most complete kit it will also come with new pan gasket and filter.
6) Once the transmission has been prepped and installed onto the engine block, you will need to bolt the trans x-member to the trans mount...at this point the trans x-member to frame bolt holes wont line up. You will need to position the x-member within the frame rails (whilst it's bolted to the tranny mount) and drill out new holes in the frame to secure the x-member.
As some extra info....The 700R4 trans bellhousing was designed to be used with "regular" V6 and V8 engines as well as "vortec" series engines, so in the future, if you want to upgrade your 70's motor to Vortec, you'll be one step ahead of the curve.