Looks like the leak was around the compressor shaft; if you replaced that seal you should be good to go. The Shraeder 'leak' will always be there since some oil comes out whenever you connect to the service port. Sometimes a section of the plumbing next to the valve will also be green where a blast of refrigerant escaped as the service connector was popped off.
R-134a retrofit setups show bubbles in the sight glass because they are not fully charged when filled according to retrofit specs. The reason for that is that running them at full charge would be an overload on an R-12 compressor and likely reduce service life. Retrofits may also show foam in the sight glass; that's due to not completely purging the old oil from the system before recharging.
Torque to operate an R-12 compressor that's been filled to 'no bubbles' or even close with R-134a may be an issue with a small vehicle engine.
The ideal retrofit is buy a complete new system for a later version of that vehicle that's designed for R-134a and mechanically compatible with what you're replacing -- not always easy to spec. Indeed there may not be a compatible later system because BTU for BTU some parts of an R-134 system are larger (at least greater surface area) than the corresponding parts of an R-12 system and a vehicle model that continued through the change over may have gotten either a fits-the-same-space system that may have either comparable or (more likely) rather less capacity, or a physically incompatible system with comparable capacity. The former you can use, the latter probably not.
Note that even though the old plumbing may be perfectly okay and all the major parts fit the vehicle in the same way, the old plumbing may not be usable in a transplant system because of differences in the connections -- incompatible dowel locations, diameters of fittings, and so on. The whole system design is influenced by the refrigerant and oil and in order to keep the oil circulating properly line diameters (and sometimes other things) have to be adjusted in a redesign so you cannot count on mix-and-match. If transplanting an R-134 system to an R-12 car plan to transplant everything, not just the obviously changed parts.
Next best to retrofitting a complete R-134-designed system is to take everything out of the R-12 system, flush the compressor thoroughly with the new oil, flush the evaporator, all the lines and the condenser with a solvent and blow out the excess with shop air, and replace the expansion valve with an R-134a valve. All the o-rings should be replaced with the green R-134 ones. Old R-12 hoses generally don't have to be replaced: They're impregnated with oil and that seems to protect them.
Of course many people just remove (hopefully recycle) the old refrigerant, maybe drain the compressor oil, add some R-134 oil, shoot in some R-134a, and go. Those people get cooling, may or may not have bubbles, and will definitely have foam from the mix of oils and a refrigerant that's incompatible with the old mineral oil that's still in there.
There's no substitute for finding and following manufacturer's specs for what you want to do.
