We have target 3.5 SP1 for a long time now so you would have to use a very old version which I would not recommend. I don't know how far back you would have to go, I know that 220.127.116.11 was the last version of mojoPortal to target 2.0 .NET, but 3.5 SP1 was already out before we began targeting 3.5 so we pretty much targeted 3.5 SP1 when we stopped targeting 2.0.
Really though, any host who will not install the service pak is not a good host and I recommend either ask them to install it or find another host. 3.5 SP1 came out in 2008, and you can be sure there are security fixes in the SP and also from updates after SP1. I would not use a host that does not keep their servers updated.
Hope it helps,