It's been a while, but I'm fairly sure the rear mount needs the sleeve in place. At the time I think it was (shorty) who I asked about it, as that's what he had to do.
Could be fun - http://www.ebay.co.uk/itm/Classic-Mini-With-Toyota-Starlet-Conversion-Round-Nose-/191564320050?pt=LH_DefaultDomain_3&hash=item2c9a1f8d32