couple of questins about engine height and sump

[flyerncle]

This may help,set the ground clearance from chassis to floor at the front on some blocks at about 5 ins and the rear at about 6 1/2ins,see what sump clearance you have and possibly fit wings to sump to increase capacity lost through cutting the bottom off. Adding 25 mm brackets to top chassis rails and adding the same to panel/scuttle/noscone height etc will give you more under bonnet clearance.

And replace the exhaust manifold bolts with studs as they always failed on the SD1 of a million years ago.

Good luck.