Not sure this is strictly an e-bike question, but it's related to an e-bike conversion so hopefully others have come across a similar issue.

I'm converting a GT Timberline 1.0 into a rear motor e-bike using a kit from Dillinger in Australia (sorry, I'm too new to post a link). I would've preferred to keep riding my very cushy Marin San Anselmo but heard you really want disc brakes for an e-bike.

The Timberline is 3 x 8 speed with a Shimano Acera derailleur and a Shimano Altus CS-HG31-8 cassette. However, the replacement wheel in the conversion kit requires a freewheel.

I can't seem to track down a Shimano 8 speed freewheel in Australia (if one even exists). The kit retailer sells a (very bloody overpriced) no-name 8 speed freewheel for more than double the price of a genuine Shimano 7 speed.

I've got a few questions:

• Once I have the new wheel on, would my existing drivetrain work if I fitted a 7 speed Shimano freewheel? Or would I have to stick with 8 speed? I get that I couldn't shift into that missing cog anymore, but would the others shift OK?
• The no-name freewheel seems to have a different tooth count (I think it's 13-14-16-18-20-22-24-28T, while the current Shimano cassette is 11-13-15-17-20-23-26-34t). Will this matter? Would I have to reindex or something?

Thanks
Tols in Canberra, Australia