LS with manual 3 speed

[LS short box]

I believe all truck LS's came with DBW throttle bodies. Camaros came with DBC.
Nothing wrong with either. I've used both with good results.
Because I'm no electrical wiz so I buy the ECM and the engine harness as a kit. I like and use Howell and Speartech. Per your engine specs they will put in a base tune to get you started. Both have good tech service if you have an issue. I would not buy a Ebay ECM/harness made off shore.
Gauges wise I've always used Auto Meter. Your stock speedo is cable driven and if your "new" tranny is the cable type you are good. Gas gauge can stay as is. Oil pressure sender can be adapted to the LS engine. Coolant sender could be adapted but I'm not sure. Can't say on the voltmeter.
The key to a good LS swap is a good harness and good grounds.