I'd go straight to talk to the likes of COME. They will point you in the right direction.

My initial instinct would be a 350ci stroker though as the Salisbury won't like much more ci that that. And if you go up to a 3.75" stroke (377ci or bigger) you may run into limitation with the HQ heads. When you are talking over 400hp up to 450hp that might also be a limitation for street use for the Quadrajet. GM used Quadrajets up to about 350hp on a small block (350hp 350 Corvette in 1969) and about 390hp on a big block. Most of the higher performance engines (like Z28 302 and 350 or big blocks 400hp and above) used Holleys, in most cases an 850cfm vacuum secondary.

COME have some specials on their website, looks like you can do a 3.75” stroker for a decent price.

Believe it or not the HQ with 350 got the gearboxes that were standard fitment for that exact engine in other GM vehicles of similar size, ie TH400 and M20 Muncie. Whilst it was down on power it wasn’t down on torque and that is what dictates what gearbox and diff were fitted. In the USA this engine in Camaro and Chevelle got a 12 bolt though. The HQ Salisbury should in theory be good for the torque of the 1971 L48 (365 ftlb from memory) but remember GMH weren’t above cost cutting on diffs and transmissions, for example the HT-HG L48 should have got a Muncie and 12 bolt, and no 307 or 308 HT-HG or LH-LX should have been fitted with a banjo. The HQ should have got a 12 bolt but all GMH did for the HQ Salisbury was to fit the cab-chassis (or TH400) uni. I think the auto cars also lost LSD.

You can help the Salisbury live by stopping the engine from producing massive off-idle torque by using a bigger cam. Places like COME will be best to guide you. If you have to keep the 10 bolt i’d also be using cab-chassis axles and bearings and sticking to non-LSD and skinny tyres.

Edited by user Tuesday, 29 May 2018 8:56:29 PM(UTC)  | Reason: Not specified