clogged water jacket in block

As if I dont have enough problems already, (see M135 Giving up, thats me)
Anyway my buddy and I are working on an old jeep. Its titled 43 but we think its a 48?
Anyway, thats not my reason for inquiring.
Last year we got it running nicly but it kept heating up and we determined the radiator was clogged, as wee as basically "SHOT".
Se now we have another foor it rebuilt and ready to go. Befor installing it we tried flushing the block which isnt too easy wwith nothing to stop the water from running right thru.
We discovered a leaking soft plug , low behind the oul fill. We took it out and it is totally packed with crud. So I removed the other low one right above the starter. W4e have cleaned and flushed as best we can.
Question is, do you think its necessary to remove the two higher soft plugs? Isnt that all open in there and should now be clean or is those other plugs hiding some pockets that are hard to get at??
Also, are there any treatments or anything I could run thru there BEFORE putting on the new radiator???
Thanks

I have a backflush tool that hooks up to the lower hose and has fittings for water and air hoses. You run the water till the block is full then turn on the air. Absent this tool you might plumb a water hose to the lower rad hose and a air hose to the block drain.