However, over the last couple of weekends, I've finally tackled the issues. To ensure a long term fix for the scuttle-to-tub squeaking, rather than applying more silicone, the old stuff was completely removed and closed cell foam padding tape went in it's place. Silicone was applied around the bolt holes on the side of the scuttle to ensure no moisture makes it's way in the frame rails, and a bead of silicone was applied to the front where the fit isn't as tight. It took a while, but wasn't that difficult. The poly bushings, however, were a different story.
My engine installation conspires to make this a big job. The alternator -- which is buried at the bottom of the drivers side and difficult to access -- gets in the way of removing a key suspension bolt, and adds a couple of hours of work and a few hundred expletives to the job. That is annoying enough, but given that the bushing grease has a short life, it means this isn't so much a repair, as it is a regular maintenance item. Fortunately I stumbled upon some grease designed for this application that people claim lasts for years, so I decided to give it a shot.
As expected, the job was a pain, and like an idiot I made
things worse. First, I damaged the rubber boot for one of the lower balljoints, and next I bunged the threads of the other when the tierod remover slipped. The lower balljoints are from an Austin Maxi which was never imported, so they had to come from the UK. But it's done. Lots of rain means I've yet to give the car a proper road test, but pushing down firmly on the frame rail is now met with silence, which is a great sign.