In a Beck you can pull the trans off the engine on a Subaru build, leaving the engine in place and the cooling system intact, and making for an easy clutch service/change/etc... You have very similar room in a Vintage, so it may be worth a shot (or just ask Greg). As for your issue, if you have a Kennedy (KEP) pressure plate I'd be willing to bet it's pulled slop into the rivets and the pressure plate is not engaging evenly. KEP still makes some good parts that I use regularly, but pressure plates are not one of them. If that is the case, swap it to a Sachs HD and continue on...