You can use the 99 subframe you'll need almost the whole front end. suspension, engine, transmission, and other drivetrain parts.
also, there will be a ton of custom wiring required. it is by no stretch of the imagination "plug and play" you need pretty much everything.
make sure that your subframe and everything that it is connected to is in tip top shape. no rust or anything. if it is, it wouldn't be a bad idea to replace the subframe mounting bolts and rubber bushings. this engine will be putting out a heck of alot more than any LN3 and since the rubber drys out, everything should be replaced. engine mounts, subframe mounts etc.
while you have everything out, it would be a good idea to inspect everything, replace anything that appears worn out. vacuum lines, brake lines, fuel lines, any and all filters, hoses, tie rods, ball joints, bearings, any assorted bushings and such. and make sure your cooling system is in tip top shape.
as far as the suspension from the SSEi. i know you can use the swaybars, and springs. if you're doing that, it would be a good time to install new struts as well all the way around. i do believe that people have mentioned that the ELC has alot to do with the handling of the car, so i will let them take you further on that in particular. but if you want a really nice sport ride with a really nice lowered look, you can always purchase the edelbrock lowering coil set. those with the fe2 swaybars would make the car handle 200% better.
as far as interior goes. they are both h-platform vehicles, so dimensions are for the most part, identical, but the design is completely different. so yes, you can use the steering wheel but it has an airbag so that would be pretty much pointless and would be a hassle to deal with as far as wiring goes. seats, i know the fronts will fit, and i do believe the rears are identical as far as dimensions go. as for as the rest of the interior, as you most likely noticed there are quite a few differences. door panels, accessories. I'm not positive, but I do believe you could actually transplant the whole dash and all of its associated wiring. this would give you airbags as well as all the other accessories if you can wire it all up right. i would recommend you have a 99 model year FSM, as well as one for your vehicle. all the wiring diagrams will be needed.
Thats about all i know. good luck with this swap! sounds great, and it will be cool to have two frankies around!
oh and please put your year and trim in your signature. thanks.