I found this on a different forum which looks to be interesting.

Here are the specs for all UR engines:

DOHC, 32-valve, dual VVT-i, chain driven, roller rocker valvetrain with low coefficient of friction roller bearings, molybdenum coated pistons with anti-friction coated #1 and #2 compression rings, available dual fuel injection on passenger car engines with single fuel injection on truck based engines, second generation high performance, low friction F head design stemmed from the GR series engines. ACIS II/III integrated into the intake manifold, which continuously varies the intake runner length depending on engine conditions and detection of air mass within the manifold. Roller rockers provide more valve lift in performance applications than previous cam lobe driven bucket type valves.

1UR-FSE 5.0L 90 degree V8 with dual VVT-i (IS500)
1UR-FXE 5.0L 90 degree Atkinson cycle V8 with dual VVT-i (LS600hL)
Aluminum block and heads
Lightweight forged and sintered connecting rods for greater efficiency, revvablility, and reliability
Lightweight moly coated pistons
Forged steel crankshaft with 8 weight balancers
Dual fuel injection with air assisted port injection and unassisted direct injection
Larger intake and exhaust ports and slightly larger valves for increased performance
Performance tuning
Estimated power:
430-450hp
400-440lb-ft

2UR-FSE 4.6L 90 degree V8 with dual VVT-i (LS460, GS460)
Aluminum block and heads
Lightweight forged and sintered connecting rods for greater efficiency, revvability, and reliability
Lightweight moly coated pistons
Forged steel crankshaft with 8 weight balancers
Dual fuel injection with air assisted port injection and unassisted direct injection
Estimated power:
380hp
370lb-ft

3UR-FE 5.7L 90 degree V8 with dual VVT-i (Tundra)
Aluminum block and heads/Cast iron block w/ aluminum alloy heads (?)
Forged, high strength internals with 6 bolt main crankshaft bearing caps, fully balanced forged crankshaft with high strength connecting rod bolts
Large diameter forged connecting rods with heavy duty moly coated pistons
Single fuel injection - air assisted port injection for greater fuel atomization
High compression relative to other truck engines
First truck engine with dual VVT-i
Estimated power:
400hp
470lb-ft

4UR-FE 4.7L 90 degree V8 with dual VVT-i (Tundra, 4Runner)
Aluminum block and heads/Cast iron block w/ aluminum alloy heads (?)
Forged, high strength internals with 6 bolt main crankshaft bearing caps, fully balanced forged crankshaft with high strength connecting rod bolts
Large diameter forged connecting rods with heavy duty moly coated pistons
Single fuel injection - air assisted port injection for greater fuel atomization
Estimated power: (bridges gap between 1GR and 3UR)
335hp
375lb-ft

Koz