I have a 351W from an 87 Crown Vic.
I am not sure what your intentions are for the 408, but for $100 I think it would be a decent deal. Here is what I am planning for my motor when funds become available:
3.85 cast stroker crank
Eagle I beam 351W rods
aftermarket pistons to keep the compression sensible
hydraulic flat tappet cam
recurved stock Duraspark distributor
stock replacement timing chain
pro topline cast iron heads
750 cfm carb
long tube 351W swap headers
Nothing too radical. Trying to maximize bang for the buck and maintain streetability. When I build the motor I plan to reuse the following parts:
Block, main bolts, timing cover, fuel pump eccentric, distributor, head bolts, oil pan and dipstick, intake bolts. I think those parts are worth $100. The swap pan, pickup, and dipstick sell for over $100 new.
90 LX hatch, TKO, carbed 302, stage II ported GT40 irons, XE266HR, Stealth, 570 Avenger, Summit LTs, H, SuperTurbos, 3.73 TC 8.8, SPECII, UPR uprs/lowrs spherical & poly, Griffen 2-1", man. rack, 26x10.5x15 ET Streets. Weighs 3060 lbs 1/2 tank no driver. email@example.com 1.751 60'