On the JLD enterprises rifles, how much trouble is it to add a navy style lower, like the ones on the vector V93 rifles?  Also, would it be possible to add a true HK lower showing all of the select fire positions, if the rifle still functions on semi only?  

tag

I am not familar with the style that Vector is putting on their 93's but here is what I can tell you.

There are basically two types of grip frames/trigger packs.

The SEF style can be a metal or plastic lower.  The trigger packs can drop in from either a metal or lower pack.  The grip frames can be SEF, SOU, numbered, etc.  Top-Notch's FBI frame I believe uses the SEF style pack.

The Ambidexterous Frame will not interchange.  It is a completely different trigger pack design

You can switch an SEF or Ambi pack as long as you are swapping everything.

If this only confused you further, do a search as there have been many trigger pack questions.

Will a MP5 housing fit on a HK33?

email victor he'll answer itfor you

Quoted: Will a MP5 housing fit on a HK33?

Yes, it will.

Quoted: On the JLD enterprises rifles, how much trouble is it to add a navy style lower, like the ones on the vector V93 rifles?  Also, would it be possible to add a true HK lower showing all of the select fire positions, if the rifle still functions on semi only?

Old trigger pack just drops into the new grip housing, But you will need to use the longer selector needed for the new trigger housing.

On converting a burst grip housing, clipped and pinned, old trigger pack drops in, and the new longer selector.  As for the trigger pack it's self, don't know if JLD adds a trigger stop, but if not, one will need to be added to prevent hammer follow threw when the selector is set to the full position.

As for the differences between a G-3 and a 33 grip housing, the tail section is shorter (only one pin), but the shorty tailed unit works fine on the longer receiver (butt stock cap still hold either of the tailed units on the receiver.