Heater core removal

I'm having difficulties finding the right water based duct sealant for this plastic ac and heater box.
Please check the link below and see maybe I' missing something?
It seems the water based ones are not formulated for plastics, like my ac and heater box?

Am looking for non harden, water based that stays pliable and can be used on plasticm but the informations they provide does not say all that.

Am I asking much? Thanks.

Slowly but I'm getting there, need help with following. The following is from ALLDATAdiy :

When all air conditioning system is first assembled, all components (except the compressor) are refrigerant oil free. After the system has been charged with R134a refrigerant and operated, the oil in the compressor is dispersed through the lines and components.

The evaporator, condenser, and filter-drier will retain a significant amount of oil, see below. When a component is replaced, the specified amount of refrigerant oil must be added.

When the compressor is replaced, the amount of oil that is retained in the rest of the system must be drained from the replacement compressor. When a line or component has ruptured and oil has escaped, the compressor should be removed and drained. The filter-drier must be replaced along with the ruptured part. The oil capacity of the system, minus the amount of oil still in the remaining components, can be measured and poured into the suction port of the compressor.

EXAMPLE: On a dual system the evaporator retains 60 ml (2 oz). The condenser retains 30 ml (1 oz) of oil, and system capacity may be 220 ml (7.40 oz) of oil.
220 ml minus 90 ml = 130 ml (4.40 oz).

CAUTION: The refrigerant oil used in a R-134a A/C system is unique. Use only oils which were designed to work with R-134a refrigerant. The oil designated for this vehicle is ND-8 PAG (polyalkalene glycol).

Front A/C

- Compressor 142 ml (4.73 oz)

- Filter-Drier 15 ml (0.5 oz)

- Condenser 15 ml (0.5 oz)

- Evaporator 30 ml (1.0 oz)

Dual A/C

- Compressor 220 ml (7.4 oz)

- Filter-Drier 30 ml (1.0 oz)

- Condenser 30 ml (1.0 oz)

- Evaporator 60 ml (2.0 oz)

- Rear Evaporator 60 ml (2.0 oz)

I don't understand all of the above information so I really need your help using what's applicable in my case, I have front a/c only. In my case, new evaporator-condenser-filter drier- and hoses. None installed yet.

I'm reusing the old original Denso compressor waiting for ordered a/c oil to start the draining the original ND8 PAG oil from this compressor and fill the system with new DEC pag 46 dyer oil. (Please advice if there are better alternatives.)

My question, from the above ALLDATAdiy info, my compressor takes 4.73 oz a/c oil by itslf or the entire system takes 4.73?

How should I start this proccess?

Thanks.

Thanks, by your calculation, rec/drier 1.0 oz, evaporator 2.0 oz, condenser 1.0 oz. That leaves 2.7 oz for the compressor. Right?