Help re cassette/freewheel......please

Having posted my numerous queries here about all and sundry, i notice that it is not only me who has queries about problems regarding the retro and the new.

My departure from cycling between 28 years ago and now has left a huge crater in my knowledge. And, the funny bit is, my old knowledge is of no use now as things have changed so much! Try explaining a Helicomatic freehub to someone aged 20 and you will understand.

Tonight's problem is unusual - i have posted previously about my rear Helicomatic freewheel and more recently about my front Campag hub. Whilst at my LBS, i asked about changing one or the other to to something more modern or changing the Helicomatic hub to a matching Campag. My LBS guy advised me that he had two unused Mavic CXP 22 rims on Shimano hubs for sale at £100. After some thinking i have decided to purchase them - it leaves me in a place where i can decide (without time constraints) about what i want to do with my old wheels and, i think, although costly, this is worthwhile. Strangely, these are the same rims which are on my new bike - and they may do as spares should i damage the new wheels.

My query for tonight is - (and for older knowledgeable people) the cassette which i will be supplied with is NEW - unlike my original freewheel/sprockets. It may require spacers and my old freewheel is an ULTRA SEVEN - which (for those of a younger age) is a freewheel which has seven sprockets BUT which takes up the space of SIX sprockets. ie ULTRA means skinny!

Has anyone any experience of doing this and are there any consequences? I am guessing that the new spindle should take 9 sprockets (on a new bike) - although they would be slim; i would be happy with 7 and no change to my chain but the spacers may cause me more sleepless nights. Is it possible to purchase a 'custom' cassette = 12,13,14,15,16,17,18 - and 19,20 if possible to replace my Helicomatic AND still have it work?

Any (and i mean ANY) advice would be greatly appreciated.

I am learning very quickly that trying to keep my bike 'retro' is very, very difficult but should i get items which i cannot use, i am trying to make sure i can get use out of them elsewhere - a pure nightmare.

P.S. If Tel is reading this - your advice is probably the most sound yet - restore to original condition!!!! (keep the incredible polishing up)

P.P.S. If this is confusing anyone, feel free to query anything

Thanks to all who read this - in anticipation.

I'm not sure about suntour ultra series, but the maillard compact series is identically spaced to shimano 7. Maillard compact was also brought out as 7 cogs in the space of standard 6. So if youre not that bothered about number of gears, I would suggest a shimano 7 speed cassette with some spacers to take up the slack on the cassette body. Shimano 7 is readily available anywhere and is relatively cheap. Try ribble, spa cycles etc

You don't say if you new hubs are cassette or freewheel and if cassette if its 7 pseed or 8 speed.
If its freewheels then they could be built to match your old ones.
Having said that I can't work out exactly what you want to do. You have new wheels, where do the old ones come in?

My current plan is to restore the bike back to 1983 condition - probably with Shimano 600ax components. I have the original wheel set - Weinmann hubs and a newer wheelset - Campag front hub, Maillard Helicomatic rear with Mavic rims. The new wheels will let me use the bike whilst i decide what to do with the other wheels.

My options are -
1. Change the second wheels to Campag front and rear or Shimano 600ax
2. Renew the original wheels - complete rebuild and a lot of polishing

In the meantime, i can use the bike with the new wheels as both the above options mean no wheels for a while.