You could have a chat to ke30turbo on these forums. He has a 4AGTE KE30, similar to what it sounds like you want to do.
Engine mounts will need to be modified in the KE30 for a 4A fitment, it's really not that much trouble though.
The engine mounting modification setup can be different depending on whether you go with 4AGZE or 4AG/4AGTE as the supercharger sits in the way of where you can bolt one of the engine mounts to the block on the drivers side i.e. in supercharged form the engine mount has to be mounted further rearward (which is further away from the original mount on the KE30 crossmember).
With the supercharger gone (4AG or 4AGTE) the engine mount on the drivers side can be mounted in the more forward position and will come much closer to the orignial crossmember mount, hence requiring a little less work to modify and will usually look neater.
So, yes there is a need for cutting and welding, get new engine mount rubbers from a spare parts shop. Don't waste your time with old ones, new ones are cheap and they don't have to be specifically for a 4A either.
Edit: oh yeah, I might be able to get some photos of my brothers 4AGTE in a KE38 (same engine mount mods you will require) next week if you still need them by then. I am away from tomorrow so send me a PM on Monday or Tuesday to remind me when I get back.