Porsche fan/engine number

[kuna]

hi, this summer I`m planing to convert my 1303 to T4 power. I`m going to use 73-78 bus engine with B.A.S, CSP or KNUF Porsche fan, I know that case machining is required... but... won`t it destroy engine number? can engine number be seen easly (without removing cooling system) after converting to Porsche fan?

and BTW whith engine will suit best my needs (2.0L, about 120PS, dual 40s, 280-290 cam) ... year/engine leters please...

thanks for help !!!