couple of points .
depending on the lower sump plate the drain bolt may hit dead centre and block your oil extension,you will need to trim the drain bolt or measure and move the oil extension up higher .
bevel opens to back of car with the tip of the extension min 1/2 " from the bottom 3/4" max.
best way to put the extension on is of course to weld it.
if its in the car make sure the extension is a tight /correct fit onto the original oil pickup,if so cut a 1/2" slot on the end going up onto the original oil pickup tube .this way when you clamp it with a hose clamp it will allow it to compress and grip .i would not use rtv there i would recomend depending on the fit if using the clamp on meathod ,loctite green or jb weld ,you will only need a thin film around the original pickup tube.
remember put the loctite or jb weld around the original oil pickup that way when you slide the extension up it will push out any extra.
let it dry 24 hrs,then accelerate