X2 on the subframe connectors, especially on a convertible. They've got a lot of flex, especially now that they're 50+ years old...
Next (actually, probably the 1st thing) is freshening up your existing suspension- new bushings front and rear; now is the time to do some reading on this forum and decide if poly or rubber is the right call for you- there's pros and cons to both. As dano said above, the Moog "Problem Solver" offset upper control arm bushings are a good step for getting some decent front end settings for modern radial tires. Don't install them according to the included instructions, this requires a different installation- again, search and read for the installation and recommended alignment settings. And don't forget the ball joints and tie rod ends, pitman and idler arms. Probably lots of 50 year old slop there.
While the front end is apart, it's a good time to box your lower control arms, and to add anti-sway bar tabs if you don't already have a bar.
You said it was originally a "275"- I'll assume you mean 273 and not 225, and have V8 torsion bars in the front. They're adequate, but only barely for a driver. Consider, at a minimum, scoring a set of factory 340 or 383 bars, if buying new aftermarket ones I wouldn't bother with anything under an inch or more- up to you and your preference between ride harshness and handling how far you need to go. Same with the front sway bar. In the rear a set of the XHD leaves would be a good starting point, there's stiffer ones but that'll be your call, just like the t-bars on front.
And tires... you need to decide how big and wide you want to go- "the biggest that will fit" isn't always necessary for a cruiser, but that's your (and your wallet's) call...
And really, any suspension upgrade should be accompanied by a brake upgrade... and that's a whole other topic... I see lots of forum reading in your future.
Snowballing? Yup. Welcome to hot rodding.
