i am puttin a 88 crx block with a 92 to 95 vtec head and my rex is a hf what do i have to change for si axles . just the hut or can i change cailper and front disc too.

 

You have to change out axles, but it seems like you are set on it.
Si. Dx, and lx all have the same diameter rotor and same knuckles/hubs.
There is no real point to having "Si" ones.
You can probably get a complete set of good knuckles for $50 or less.... maybe free if you search enough. Paying that will be a couple dollars more than what it will cost to buy the new bearings to have the hubs replaced with Si ones.