no need to seam weld anything, you will want beefier mounts though, 16v or G60 should do it. If you're using the vr6 brakes ( you really really really should upgrade your brakes somehow) then you'll need to do a hub swap or just use the entire vr6 drive train, either way that will leave you with 5 studs at the front so your wheels wont go back on

wiring shouldnt be too much of a git since you have a 90 spec with the later loom already
your front suspension will be as useful as a chocolate teapot too, get it swapped.