Advice on spacers

Right, before I post pictures of my new aquisition I want to get it on some better wheels. The wheels I have are not Japanese exotica or anything but they are a very nice set of 17's that I bought about 10 years ago and fit a standard car perfectly. 7jj front, 8jj rear and staggered rims aswell. The offsets on them are 40 rear and 42 front so I have calculated a 39mm spacer rear (33 offset different plus 6mm difference in width) and a 29mm front. Given that these are not off the shelf sizes I would have to go for 40mm and 30mm but should I go more or even less? Is the standard fittment enough to really fill the arches on a 17 inch rim?

Fully adjustable suspension on it at the moment, I am not interested in a super low car or one with 'poke' or 'stance' I want it to look right like it could have come from the factory like it.