i believe it is a close fit, but not exact. if you are looking at this as an upgrade option then forget it, as i think they are both t-series and the brakes on the 81 are not significantly better. that is unless you find a gt model with lsd in which case the upgrade is well worth it
and also the engine is an R series, so no it will not fit straight in and there is not really much point in adapting it either with the high availability of t series motors