Re: 351w or 460?
First, check with local emissions laws. You might be better sticking with the 351. With it being a 1979 460, the 351 more than likely puts out more power and similar torque numbers. I'd leave it as is and part with the 460. Electronic complications might also arise, as if the 1990 has OBDI then it won't be feasible as the 460 isn't electronically controlled.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!