I'm not sure how many people would still do this anymore when everything is LS powered these days but I figured would document this just in case someone else is as crazy as I am:
My Engine:
61 Buick 215
98 Rover 4.0 heads gasket match ported (higher compression, larger valves, accessory mounting bosses)
77 Buick V6 w AC water pump
77 Starfire Buick V6 w AC front accessory brackets & pulleys - PS, Alt & AC
Gasket match ported stock 215 intake manifold
Buick 300 exhaust manifolds
Stock Buick V6 rubber motor mounts
What works without changing
The 215 with the V6 motor mounts bolts right into the car on the V6 frame mounts. The tranny mounting face distance is exactly the same as the 231 V6 was, so my T5 tranny still fits (just barely)
No issues with the power brake booster, master cylinder etc.
No issues with the AC except that the high pressure manifold hose is now too short
What doesn't fit & needs modified
The 215 oil pan hits the inner tie rods & center link. The front of the pan needs to be cut & welded shallower.
The engine ID number pad on passenger side hits the accessory brackets & needs to be shaved down.
The 3 V belt lengths are slightly different
The starter solenoid hits the frame. No one modifies these old starters any more so I had to get a mini starter from D&D and re-clock it.
The steering shaft hits the exhaust manifold at the steering box end. I went with a small steering u joint.
The power steering pump hits the exhaust manifolds - I could not find a way to make it work.
I switched to manual steering and even this box makes the u joint hit the manifold - I had to shim the steering box at an angle.
You need to use a manual steering pitman arm & center link but this hits the drivers side engine/frame mount. I had to clearance the mount.
The 215 oil filter housing makes the filter hit the idler arm. A Buick V6 housing & filter works perfect.
The V6 filter housing had to be drilled & tapped 1/8 npt for the oil pressure switch
The water pump pulley is very close to the radiator. I cut the water pump shaft shorter and used 2 small electric fans
For upper radiator hose I used the stock V6 hose and cut about 4" out of the center of it and a bit off the radiator end.
For the lower radiator hose
One of the AC compressor mounting brackets is in the way of the lower radiator hose. I cut & fabricated a Z bend in it.
The long arched alternator mounting bracket had to be cut & modified to fit the water pump mounting position properly.