The engine build in that 84 G20 is pretty mild but capable of more than 400 hp. Looks pretty much stock externally save for the GMPP vortec intake and larger 2 1/4" exit log manifolds with a P30 van EGR tube. Even used valve cover adapters to use the OEM van perimeter bolt valve covers. The 350 vortec block used had a fuel pump hole machined so it has a mechancial pump. Just a 350 vortec block, 0.030" over with flat top pistons, 0.016" steel shim head gaskets, slightly cleaned up 906s with a little bowl work, exhaust ports ported, the valves deshrouded and 1.60 exhaust valves, comp 787 retainers, pac 1218 springs and 0.050" offset locks. Screw in-studs and guide plates as well as hardened pushrods and narrow body non self aligning 1.6 rockers. Cam is a Melling 22280 with 220/224 @ 0.050 duration on a 110 lsa (lift is 0.528/0.535 with the 1.6 rockers). Compression is 10.4:1 and the HEI has been recalibrated with a conservative spark advance curve and the ESC knock sensor system from the 305 retained. With a 700r4 and 4.10 rear geat it will have some nice get up and go and still cruise nicely with the a/c blasting. Should see around 18 mpg at 70 mph with the cruise set. Added a MSD 6 box and a timing control knob that allows timing adjustment on the fly. Set the base timing with the knob in the middle of its travel and you can advance or retard the timing on the fly with the twist of the knob. It is setup to run on 91 octane with the knob in the neutral position, can get away running 87 with the knob fully retarded 7.5° and run it at the track on C16 with the knob advanced 6°. Van had a fuel switching valve from a C10 and a smaller fuel cell that holds race gas under the back in addition to the standard tank. Drive it to the track on pump gas, couple of miles before you get there, switch to race gas and ready to run when you get to the staging lanes bump the timing.