Oh its already engineered for a CA??!!
In that case yes go CA18DE with quads and a very good
tip from an ingenious racer is you can go solid lifters
by using Toyota 1zzfe engine factory solid lifters which
supposedly are a straight swap! cheaper than Nismo & others
by 400 bucks or more in some cases.
You should definitely go bigger bores and send your head
to Steve Newing who was able to get 240+hp out of them.

H165 has ring gear diameter of 165mm or 6.5 inches
The Quickchange is 7 inches and in the wiki the
H165 open diff is 52kg. My Alfa lsd with sump and cooling
fins was about 56kg & I think 7.25 inch ring gear with
adjustable torque biasing but a quickchange has the
beauty of the 2 ratios for track and street and nothing
comes close to that beauty.