Track width with cpp drop spindles

[70sangersean]

Hello everyone.
I've searched the web, forum and talked to CPP and porterbuilt and still have not gotten a definite answer. I'm sure the answer is out there, but I haven't been able to find it. I have a 71 c10 and want to know if the CPP 2.5 drop spindles (non modular) will change my track width. If so how much ?increase or decrease ? The wheels I want are 20x8 (don't have 8.5) and only come with 4.5" bs. From what I've read a 5.25-5.5 bs is ideal. This truck will have a 4.5/6 static drop. I will be ordering porterbuilt control arms and need to know whether or not to get the 1" narrow ones. If my math is correct and the track width remains the same as stock going with the 1" narrow control arms should put me around .5" to the inside of what is ideal. Then I could space the wheels out if needed. I know putting the spindles on and making sure myself is the best thing to do but if some already knows then it will save me the hassle. Also what would be the tallest tire I could run with out rubbing ? 245/45R20 ?
Thanks for any help in advance.