Just a note so that you're clear on one thing... the SR20DET that comes from the Silvia (240sx in the US) is Rear Wheel Drive. So it's not a consideration for our cars.
There are actually more engine choices than what has been outlined.
If you're interested in doing a lower budget swap, I'd look at going with an SR20DE (again, from the Sentra/200SX SE-R's). You can find plenty of information on what bolt-ons work. Basically you can get to about 150-160whp without having to replace the internals (other than cams). Also, as the SR20 series motor is a turbo motor, it's very easy to turbo... it's closed deck design is NICE. You won't find the same problems you had with the B-series honda motor... no open deck. SR20DE's respond very nicely to FI. The rods and crank are amazing for a stock NA motor.
If you want to stay all motor but are looking for something with more potential than what an SR20DE can provide... look no further than Nissan's VE series engines. Think of them as Nissan's answer to Honda's VTEC. There are 2 basic choices for us.
The SR16VE which puts out a rated 173hp @ 7800rpm / 119lb torque @ 7200rpm, and
The SR20VE motor which puts out a rated 187hp @ 7000rpm / 145lb torque @ 6000rpm at the crank.
A few owners of the SR20VE are approaching the 200 wheel hp range with only the typical bolt ons and cams.
There are also three other motors in the SR-VE series that are of interest, but unfortunatly are not really an option right now.
The SR16VE N1 - 197hp @ 7800rpm / 134lb torque @ 7600rpm
(Nissan's Answer to Honda's Civic Type R motor). Good luck finding one...
The SR20VE - 204hp 6 speed Manual 2001-Present. Again, good luck finding one right now... they'll start to come over eventually.
and
The SR20VET - 276hp @ 6400rpm / 228lb torque @ 3200rpm
This comes from an AWD sport utility... Why? Who the heck knows. Nissan can be stupid at times. I've never heard of anyone adapting one of these for a FWD car... and for the money that you'd spend doing it, you could of made a lot more power out of one of the other choices.
For our cars, there are actually two DET motors... the SR20DET from the Bluebird and the SR20DET from the GTiR. I don't know all the differences off hand... so you'll have to research that yourself. I can say the GTiR is the more tricked out motor... but also the more expensive one.
Hope that helps... if your interested in more information about the VE series motor, a good place to check out is
www.sr20deforum.com