I would definitely consider reinforcing that front end for several reasons: 1) you've added considerably to the total weight of the vehicle; 2) regardless of how good a job you've done structural integrity has to be weakened somewhat by the clip graft and 3) that powerful SBC is going create some significant torsional stress on the frame. My advice box it.
Good luck


Steve G.
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1942 Chevrolet 1/2-Ton Pickup Truck