I posted a topic here somewhere last year about a LG3-3 a LeSabre T-type owner was building or built I should say. I just cant remember the subject I used for the post or if I threw it up on some other post about performance
Also one about a turboed LG3-3 in a Fiero
Anyhow he had comp cams do a new cam from a blank so there is now a part number for that cam I just dont have a link
The cam is most of what causes the low HP RPM. Its not the largest throttle body either but theres not much to do about that. The turbo Regal guys do not use high RPM'* either, in fact I think they shift around 4000 with the production engines, stage II engines might be different but not the production street car engines. I have a turbo Riv engine ( same as turbo Regal except manifold layout) and they do not have large tubes either. I believe this actually helps in the low RPM torque, thats what a old 3.8 needs to be built for, more torque and low RPM power curve, because that is how it was designed - its a B U I C K
Heads can be ported
The rear exhaust manifold can have an obstruction near the down pipe. Its the easiest exhaust in the world to remove. If you take it out and look up in the rear manifold you will see the problem and a long shank burr in a die grinder can work wonders and its a quick job, just wear safety glasses because your kinda vulnerable down there.
The turbo guy put aluminum heads on the LG3-3 block. He also said the crank and rods were strong enough as they were, as good as the RWD turbo engine had I believe. Its probably a weaker block though.
pistons I cant remember anything about but I believe both builds used other than stock pistons.
Absoultely nothing off the later 3.8'* will fit on the early 3.8'*.
Its not the most perfected of the 3.8'* but it sure is the purtiest !
Hope this helps, its all I know and its not hands on, its from reading and asking questions, all my engines are still stock, except for the rear manifold issue and intakes/air filters.