The engine will bolt in, but it's a little more involved than that. You have to relocate and redrill one set of holes. Also the 110 is a little longer than the 70 so you either won't want to run a front fender or you may want to lengthen your frame. You probably should install a front engine mount since the 110 is heavier than the 70. And except for the wiring harness and electrical parts for the 110 engine, you might like the 110 handlebars better. And that's about it. Also I forgot, you can use the 110 rear bearing carrier, but again you have to redrill holes and then you could use the 110 rear axle. I haven't done this though but have read about it from greenhuman.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90