Jumping into the deep end!

[jmpsebring]

Hey everyone, I just received my Scania R620 and I plan on converting it to a longline version. I may have no RC truck experience, but I've built a few rc on- road racers and been a dedicated model builder for 50 years.
That means I have spent countless hours looking through build threads and ebay candy stores Unfortunately I stumbled upon a certain Corvette hauler on Youtube and was blown away. So while my brand new Scania kit landed on my door, I spent ALL night last weekend exploring the real & RC custom Lo King haulers. A smoking bank account later and way too many orders from SemiJoe's and others...I have most everything needed to make my own stretched custom show truck, all decked out in hi quality parts.
Here's my first need for RC advice. This wont be used often as a RC truck. It will be mostly a show truck model that also runs. I don't think 3 speed transmissions and MFU are needed for this truck. They will take up too much room as I plan on making the extended sleeper detailed, as opposed to a place to hide items. Are the smaller planetary/motor packages something to consider?? Do they have reverse? Are tiny Futuba R603FF 2.4FASST receivers and my Novak GTS esc's perfectly compatible with the stock hi torque very low speed Truck applications? These are things I have used in carpet racing years ago. I look at the prices of some items today and they are way cheaper than the extra light, super fast, hi-amp brushless race components I have sitting around..virtually new?
Not opposed to buying a new radio/xmitter because I'll need one for my Scania/MFU truck. AM stick style.
Advice??? Any build thread that addresses this very concept of minimal hidden electronics?