Just be carefull not to go too low with the profile of rally tyres. If you do, then it is more likely to have problems with large rocks damaging rims because there is not as much of a 'buffer' of rubber between the road and your rim. I use 165/65x14 tyres and have had very few problems with them.
I am also lucky that we have a retreading plant in NZ that make a very good M&S type retread. I provide my own rally cases and get them retreaded for around $40ea. I have had between 4-5 recaps per case so far without any failures. They are fairly soft tyres and they do tend to go off after around 20-25kms depending on the surface but I still swear by them. We have still done 50-60km special stages on them beating all other 2wds so they can't be too bad.
We are looking at between $190 - $300ea for new 'brand name' equivalent tyres here so I am quite happy to continue using what we are using.....besides it is GREAT to kick arse on supposidly inferior tyres