Many people have tried to install wiring kits in 335-style guitars by inserting the components through the F-holes. This is generally unnecessary, as most guitars of this style offer access to the control cavity via a hole beneath the bridge pickup. Not all guitars do, we have seen guitars where there was no way into the cavity except through the F-holes, but in our experience this has been the exception rather than the rule.
The components from the American brands (primarily Switchcraft and CTS) are larger than some of the imported components, especially pots. Many guitars come with pots that are roughly the diameter of a US dime, whereas most CTS pots are roughly the diameter of a US quarter. So the original components on some imported guitars might have been inserted through the F-holes, and if this is the case then getting the larger CTS pots through there is probably just not going to be possible.
But check under the bridge pickup. You might just find a nice large opening there that allows the entire wire harness to be slipped into the guitar easily. Or, you might find that there's a an opening there that goes into the cavity, but it's too small for the larger American components. If this is the case then you'll need to find a way to enlarge the opening. This might be easy, you might be able to use a small saw, files/rasps, or a Dremel tool. But it might be that the hole is hard to access, in which case you'll need to be creative. But in the end, it's worth the upgrade if you can manage it, as the components in our wiring kits are far superior to the original components in most imported guitars.