The '86-'87 TBO-348 turbo could typically support around 465 flywheel hp if pushed to it's limits. The turbine housing would bolt up to your existing header/up pipe, however, the compressor cover that is used on the '84-'85 Hot Air cars' turbo is very different than the one used on the TBO-348. The HA version is an o-ringed, slide in discharge out of the compressor cover into the upper plenum, where as the TBO-348 has a clamp on hose style discharge. They are not compatible without some serious modifications being made.
I don't think Garrett ever published official CFM flow ratings of each year model turbo. But, due to the size and design of the HA turbo, I wouldn't try to push it much past 350 flywheel hp.
Here is the link to the '84/'85 stock turbo.
Turbocharger Guide
Some pics,
Here is the link to the '86/'87 stock turbo.
Turbocharger Guide
Some pics,
Stock turbo on the right in this picture.
The other difference, obviously is the clocking configuration between the two are totally different. An '86-'87 could be clocked in the same manner as the '84-'85, but would require modification to work with the stock hot air intake manifold. Boost levels for '84-'85 were 7-10psi ambient temps depending, and '86-'87 levels were 12-15psi ambient temps depending.
Hope this helps.
Patrick