<VV> 140 engine codes RB- RM differences?

[Sethracer at aol.com]

Mark wrote:
 
What's the difference between the RB and RM engine codes on the 140?  I 
know that both are manual and that the RB is Corsa, but what are the  
differences between them?


And Matt wrote:
 
The cylinder heads have different threads / hole depth  for the  temp 
sensors.... for one


So Seth writes:
 
I do not agree, Matt. Both in the parts book and by my  experience, all 
140HP, 150HP and 180HP heads were drilled and tapped for  the 3/8-24 thread 
used on the thermistor. That is why all 140,150,180 heads take  a different 
temperature switch for the passenger side. According to the parts  book, all 
Corvairs except those use one temp switch. Even when used in a  Monza or 500, 
the fine threaded switch was used with the 140 motor. They just  left the 
drivers side threaded hole empty. 
 
As far as the differences, as mentioned, the shroud would have  no hole for 
a temp sender feed. I suppose the intake manifold crossover tube  would 
have no fitting for the gauge feed. And if the air-filter housing is  included, 
it was only chromed on the Corsa, as I recall.