I have to agree with Gold28 on this, the 1UZ will be the go as long as you can get around the engineering issues
Weight should be close to or lighter than the original motor
It should fit without firewall mods maybe just a little releif where the starter buldge is on the top of the bellhousing to allow the box to slide in and out inedpendant of the motor
but this will depend on how far you want the motor back
Rocker covers will slide under the brake booster and clutch slaves
I'm not sure on what sump you would require in a RA28 but someone else maybe able to help as there are 3 sump options
I don't know this one for sure but i have been told that if you offset the motor slightly you can squeez the exhaust out past the steering box ,..in my case in the 22 i have a rack and pinion and didn't get the chance to check if this would work , besides the 28 has more room so it may work
but either way any of the v8 will require a bit of work to fit