Hello, Im planning on lowering my C63 Sedan with H&R springs but spacers wise can anyone please give me input on size and where to find the right bolts.

I just did 15mm all the way around and will likely switch to 10mm rear, 12mm front.

Spacer sizes also depends on tire size.
10mm on rear is fine with 255 but if you want 265-275 for better traction then you'll need to stay with a thinner spacer.
Unfortunately 10mm is the thinnest hub style spacer and also the safest way to run spacers.
With the rear stock ET54 you can run a 4mm spacer and still have hub to safely rest the wheel on.
12mm for front is fine with 235 tire but a 245 would be better with 10mm.

I will likely do 10mm rear and 12mm front I have 235 upfront aswell as 255 in the rear, just need help with what bolts to get.

The stock bolts are 28mm so you will need 40mm for the front and 38mm for the rear. You can go a little longer on the front but not too much more on the rear. If you go too long on the rear the bolts will hit the the parking brake parts inside the hub. Turn the rear wheels after you tighten up the lugs and if you hear a ticking noise they are too long and you will need to cut or grind the ends back a little until they no longer contact anything inside the hub. Be sure to get 10.9 grade bolts.

Here is a good site to begin your search: https://otisincla.com/

If you are not sure what bolts you need give Phil a call and he will be happy to help you out.

When I had the car. H&Rs w/17mm rear spring pads, PS4S 265/235, 15mm front, 12mm rear spacers. No rubbing.

That set up looked really good.
Both F&R seem to have a fair bit of negative camber

Thank you!